Johnson, Evinrude, OMC, outboard motor, outboard motor repair, 9.9, 15 hp, date/year of manufacture, water pump, carburetor, long shaft, 15 hp conversion, sailmaster

Note -- some of these articles have pictures that require a possible long load time, especially if you are on a dial up connection
 

For those of you who may not be aware, Outboard Motor Corp  (OMC) was a company that was formed from by combining both Johnson & Evinrude products.  After that point in time, the only real difference was the color of the paint & the decals on the motor.   So what you see here that says Johnson, also pertains to the same equivalent Evinrude motor.
 

This article covers many aspects of these series of OMC motors, but over the years it has grown to the point that I have had to split it into separate specific sections.  In doing so, you will see a CLICK HERE or  Yellow Highlighted underlined link that takes you to the article that is specific to what is being discussed.  Some links to online information will have the link in an underlined blue color.

 

These outboards, like any that get used & or abused may need to be torn apart & repaired over time.  As they get older, the depreciated value of a somewhat neglected/abused motor is such that with a motor in the 25 to 35 year old range, it could be questionable as to whether taking it to a outboard mechanic is worthwhile for other than electrical trouble shooting type of repairs.  Most shops now charge from $85 to $90 per hour.  Some shops even refuse to work on anything over 20 years old.  I have seem some newer abused motors that I would not pay $50 for, & then again a older one that has been used but maintained, may be worth from $500 to $1000, depending on the year, compression, & whether it is electric start & a longshaft or not.  It is my observation that most outboard motor problems are not that the motor is worn out, but it is the NEGLECT / ABUSE  & lack of care it received over it's lifetime.  Outboard motors don't just die, their owners kill them.   An older well cared for motor, is worth way more than a newer neglected / damaged motor.  These series of motors are almost bulletproof if at least some resemblance of care is performed on them.

This article is not meant to take the place of a service manual.  It however has some tips from my personal experiences & other information that has been gleaned from many sources over the years that may make owning and /or repairing your motor a little easier to understand.  It started out as a documentary as to what I had learned on my own motors to myself, as I seemingly have become more forgetful as I approach 75 years of age. 

 

Most commercial outboard mechanics have to work on many different makes & sizes of motors in order to make a living, therefore it is unreasonable to expect them to remember the whole history & the little extra things to look for when repairing one particular make & model.   Hopefully this article will help those of you who do decide to "DO IT YOURSELF".

If there is any chance that you do decide to work on it yourself, it is highly recommended that you purchase one of the excellent illustrated service manuals (preferably the factory ones for your specific motor) that covers your motor before you venture too far into trying to repair something you may not be that familiar with.  It is also highly recommended that you get a factory parts catalog for the year of motor in question.  However many of these shop manuals are written for skilled/trained techs who already know most of the workings of these motors so will leave the novice scratching their heads at times.  But with these manuals you can see the exploded view of the parts & can order by part number. The part numbers may have been superseded, but the shop you go to when ordering parts, can cross-reference to the new number.  This parts manual also helps you positively identify the part you need, as compared to ordering something by the wrong name & getting the wrong part.   Remember, most of mechanics/counterpersons flunked mind-reading school.  These parts manuals will also provide a picture placement of the related parts.

One source of original or reproduction manuals would be to go to www.ebay.com & then type in outboard motor or 9.9 johnson as a search.  Used original OMC parts manuals for these motors usually go for from between $5 to $20 & are more in demand than the service manuals.    Original, or copies of OMC Service Manuals for the year motor you are working on would be best.  There may be some latitude as for years if it is close to what yours is, with the exception of the 74 thru 76 electronics, being on their own as compared to the later electronics.   Undoubtedly the parts manuals are very important to the home mechanic.  Another thing that can be invaluable is a digital camera.  If you tear it apart more than just to replace some small item, take a few digital pictures of the motor with the cowlings off. 

 

The service manuals are very helpful & explain in detail just how to repair the motor.  You really need both the service manual & the parts manual. 

Owners manuals do not really help you when doing repairs, they just give you pointers on how to adjust carburetor, the trim & how to jeep it clean.  

Also be aware that when you go to the dealer to order parts, that many times some of the larger dealers would rather you brought your motor in to them to work on.  Remember that they need to keep their employees on the payroll.  Therefore they possibly may resist ordering parts for you saying they are hard to find.  Or if they do accept your order, they may not place your parts order at the top of the "To Order" priority list, since you are planning on doing the repairs yourself.   However if you go to them with part numbers they may be more obliging to place an order, since the monkey is on your back for providing the right or wrong part numbers, & you are then obliged to pay for them even if some wrong parts show up.  However, if you do come up with your own numbers, also have the description, so they have some idea of what it is.  It would also be best to indicate which year of parts list you used, as many of these older parts numbers have been superseded by newer numbers.  

Another thing to consider is that most times the manufacturer or distributor like to have an order from the dealer in minimum quantity or dollar value to cut down on excess shipping.  There is the possibility that the dealer may have just placed an order & will not place another until they get enough accumulated to qualify for another order.  They will undoubtedly want you to prepay for the order.  Also when the order comes in, even though you requested them to call you, with possibly more than one person in the shop, that information may have gotten misplaced.  They should be able to give you an estimated delivery time.  However don't call them & inquire for at least for a couple of weeks.

You can look up needed replacement parts & order online thru this LINK.

I am not an outboard mechanic, but a retired machinist who has been working on this series of motors exclusively for over 30 years.   If you are like me, & do not have anywhere near a photographic memory, by the time you tear it apart, get the parts ordered & then try to reassemble it weeks later, you can not really remember the exact sequence or placement of some critical parts.   Also someone else could have worked on it in the past & the part may not be where it actually belongs.   Most times you can figure it out by trial & error, but proper placement of others that may be somewhat internal, where if you guess wrong, may require the whole engine or lower unit to be disassembled again just to reposition or add one forgotten part, (been there-done that) which can be frustrating.  This miss-placement of a part will usually come to you some time later,  & usually in the middle of the night.  With the digital cameras commonly in use now, this may be a good way to record what things should look like before or while you take it apart.

This is Not Really a Trouble-Shooting Article :  You will find my troubleshooting article by itself.  In the following information provided in this article, it is assumed that the motor is in a good enough condition TO run.  If you have bad spark plugs, rings, carburetor being fouled, or anything that may contribute to the engine not running then you will need to address that situation, especially as a pre-requisite to doing anything else.  Any work needed should also be done in addition to what  is covered here.  AND, we are assuming that you have the motor mounted on the boat transom properly with the cavitation plate even with the hull's bottom & the motor tilted at an angle that lets the cavitation plate be straight with the bottom.

 

All the above said, if you happen to be one of those persons who should not be left alone with a pencil sharpener or even sharp knife & do not have the ability to read & at least comprehend even the least bit if information, it may behoove you to not try to work on your own boat, motor or trailer.

Free Advice : You may find persons who offer free advice on about any subject, outboard motors "experts" are no different, but I have found that MOST of these Good Samaritans may not be as good as they think they are.   Some like to talk just to try to impress people (I call this BULL SHIT).   If you happen to frequent some of the boat or motor message boards, you will soon see a response to the question of a motor not running exactly right.  The most common response is to rebuild the carburetor.  OK, this may be part of the problem, but it is not the cure-all, as your problem could also be ignition or compression related.   Another response often seen is that you should replace the water pump impeller every 2 to 3 years, just a a precautionary measure.  This might be so, IF you are operating in VERY MUDDY, SANDY or debris infected water, OR are using it as in a main motor that is used MANY miles offshore.  The current new impellers should last for MANY years if the motor is treated right.   I replaced one of mine after 20 years, it was still intact & functioning, but to what degree of originality I could not tell, (memory problem for a 74 year old geezer).   It however was not as pliable as the newer one I replaced it with.  The reason I replaced it is that I was adding a long shaft unit & decided while I had the lower unit off, that I has just as well replace the water pump impeller at that time also.  However any impeller could be ruined after only a few seconds of running without water (also been there-done that in one of those brain fart instances).

 

A few years ago, I purchased a 70 hp Johnson from a private individual, when I was looking at it prior to the purchase, I asked if it ran, he immediately reached over, twisted the ignition key & started it, (it was still on his boat & trailer in his driveway).  THE MOTOR WAS NOT HOOKED UP TO WATER MUFFS.  I quickly told him to shut it off, his reply was, that's OK, I ran it like this yesterday.  I immediately looked under the hood for evidence of overheating (which there was none) but deducted $100 off my offer.  And YES the impeller was totally demolished, having the tips of the vanes worn off enough so that it would have pumped very little water while plugging the water tube with ground up rubber if it did. 

Proper Repairs ?? : There are many ways to repair anything, with outboard motors not excluded.  You can skimp by & just repair or replace what is needed to keep it running & there may be a place for this type of repair.  Or you can go one step farther & clean up plugged water passages, or replace any other parts you find that are not really up to par.  This extra could be a frayed starter rope, a hardened fuel line primer pump, twist grip throttle gears that jump out of mesh, or a leaking gearcase drain plug seal.   I for one do not like the idea of fighting my motors just to get me to, or more importantly, getting me back from the fishing area.  This can also cut deeply into your limited fishing time.  It is a lonely feeling to be dead in the water, and paddling against the tide or wind is not a very rewarding situation, it may however become exciting.

Most parts for these motors are still available from different sources, either new or used, however price may be prohibitive on some cases.  With this in mind you may consider making or repairing your own, or purchasing replacement bolts from the hardware store.   Now I am not saying to tie the broken twist grip handle on with bailing twine, but I am sure human ingenuity can prevail if the need arises.

The mechanical repairs are a usually no brainer, but electrical problems can well be aggravating until you get them figured out.  And since you & I do not normally have lots of new or even used parts that are known to be good, it is hard for us to simply swap out parts until we find what is wrong.  One internet parts supplier includes a sheet listed below with their shipped parts.
 

"---WARNING --- The outboard marine ignition system is one of the more comprehensive electrical designs in the market today.  The most common error made by the mechanic or the owner is to simply replace a defective component within the system without determining what exactly caused it to fail.  "Did a shorted rectifier cause this problem?" or "Did the owner charge his battery improperly?" ; are just a few questions that reflect a couple of the many possibilities for failure.

  Make sure your part is defective for the right reasons.  Always consult your maintenance manual to see that the part you are replacing is the problem and not the result of the problem.  If this is not done, failure will only happen over and over again."

Spare Parts Availability :  Most marine repair shops even though they may not be a OMC/BRP dealer, can get parts if they want to.   However a big Honda or Yamaha dealer may not be interested in helping you in the least, where a smaller independent mechanic may.   The one online marine dealer that seems to have factory parts for most models is http://www.boats.net/ .  Their website has a online illustrated parts listing.  Their parts are discounted off retail prices.  They even have a parts technician that you can call to verify if you encounter any questions.   I am not sure how old of models that they carry parts for, but I had no problem getting water pump parts for a 1977 Mercury 4.5 hp.  They then ship FedEx.

Here is another source where you can look up needed replacement parts & order online  http://www.marineengine.com/parts/parts.html .

 

Also, you can go to any Car Quest automotive store & request a "Sierra" marine parts catalog.   NAPA  also has a "Marine Catalog", which by the way, uses the same parts numbers as the Sierra catalog.  These catalogs will not have all the specialized individual parts like motor mounts or decals, but they do list most pistons, rings, bearings, gaskets, seals, water pumps, fuel pumps, impellers, & many ignition parts.  They also will not have current production parts within the last 5-10 years, making you go to the marine dealer for them. 

 

The one thing about the above catalogs however, you may need the manufacturer's parts manual to give you some of the original part numbers, to properly identify the needed part.   But also bear in mind that even OMC changes / updates part numbers.  This means that the number you get out of a 1983 OMC parts book, if the part is still available, may be changed to a totally different part number.  So to help the dealer, you also need to identify the motor & year of the motor in addition to your part numbers so if you got the number wrong or the part may be obsolete, the dealer can look it up in the current parts/price update list to get current part numbers if applicable.

 

Since about 2003 prices for replacement parts for these old motors from Bombardier has raised many times.   It seems when they are getting low on these old parts the prices just keep going UP & apparently they have no intention of reproducing them.  Some of the normal more in demand parts are rather expensive, like the mounting clampscrew assembly & the upper motor mounts.  Therefore used prices have begin to climb even on e-Bay.  

 

Bombardier Recreational Products Inc. now has a online parts listing for both the Johnson & Evinrude at http://epc.brp.com/default.aspx?brands=ej&lang=E&dealerlocator=no.  This has a complete listing of parts, with printing off the illustrations possible.   It also has a pick list, that you can print off.  However I have not found any prices, so this must be just that you have the part number information when you go to your dealer.  This will prove to be very helpful in allowing you to decide what parts you need for your motor.   One word of caution, in my effort to research the inner exhaust tubes for the 9.9/15hp, it appears that the actual illustrated parts are not necessarily the exact picture.  The part number is correct I am sure, but the picture may be misleading.

Some Shops Refuse to Work on Older Motors :  There may come the time when you do need to take it to a marine mechanic, because you simply do not have enough spare parts to exchange in testing, or the needed electronic test equipment to diagnose a ignition/electrical failure.  A few years ago I ran into a independent marine dealer who informed me that they will not work on any motor over 20 years old, this 9.9 OMC included.  Their explanation was that parts for many of these older motors are not obtainable.  I had what I thought was an electronic problem & in the year 2002, I took my motor in & presented this dealer a complete list that contained the motor year, model, serial number & all the previous repairs & the things that I had done to the motor, like compression test, spark jump test, how it was acting etc.  Now, their refusal may be understandable in one sense, but for this particular series motor that had not really changed that much during a time span of 18 years, with the last of this series being made in 1992 (only 10 years before), and with parts still available from Bombardier, it seems like they are not really interested in giving service.   And I for one will seriously consider whether I need to patronize them again, unless it is an emergency on my part.   Recently I have heard of another shop doing the same.  My suspicion is these shops are not run by the owners, that their mechanics are of the younger generation & have not been trained on these older motors.   And they consider these older motors only good for anchors.

 

I recently talked to an independent mechanic, but this time a late 9.9hp Mariner 4 stroke that was equipped with a Yamaha powerhead that he was working on for a customer.  This would have been common in that Mercury used the Yamaha powerhead on their 9.9s up until recently.  This same above mentioned dealer refused to even offer any advise as to a choke solenoid problem & even told the mechanic to never bring it in or even bother him with this JAP import again.   Now this is odd in that this dealer is still a Mercury sales & repair dealer, and even has many certification plaques on his wall.  OH well, he must have enough business that he doesn't need more, AND/OR he really doesn't know how to work on these motors to start with & is smart enough to not want to show his ignorance on this subject.
 

It seems that we here in the US are spoiled by being able to at least find a marine repair shop within a reasonable driving distance.   In other parts of the world, they are non-existent & if you do find one, the word is that service is lacking possibly because of lack of parts availability, or that they do not see as many of these US motors & knowledge is lacking.   In my previous service repair type business I made it a point to not charge my customers for my learning experiences.   I just heard from a friend in Germany where outboard mechanic labor equates to $125 per 15 minutes work.
 

Since I have had these articles posted on the internet, you would be amazed at the pleas for help that I get from all over the world.  Most of these requests for information are covered in my articles, just written a little different format than the question.   Or they did not read the whole article or related ones.  There is a lot covered here & needless to say may need to be re-read numerous times to digest something that the average person may not be familiar with to start with.

Story #1 --   I had acquired a used 1974 "rebuilt" powerhead off eBay that was supposed to have run hot after a recent rebuild.  The owner got exasperated, stripped the motor down & sold the individual parts.

When I got it, & since it was just a powerhead & readily accessible, I wanted to find out any potential problems before I put it on an ailing motor that I had acquired earlier.  Upon disassembly, I discovered that YES, it had seen a wrench before.  Namely a different (red) gasket sealer material under the head gasket, powerhead to upper housing unit & also under the water jacket, indicating that someone had at least had it somewhat apart & looked at it in the not to distant past.  I did also find evidence of the same gasket sealer in between the front & rear sections of the block, so at least the block had been apart & possibly there were new rings put in.  OH yes, and it had a recent gray paint job.

The head & head gasket came off the block OK, but the head gasket was still stuck to the head.  The previous mechanic had not removed the gasket off the head in an apparent attempt to do a cheap overhaul by using the old gaskets.  The suspicion on my part was that this was probably because they were afraid if they tried to take this gasket off the head, that they would ruin the gasket & could not use it over again.  There was however new sealer material between the gasket & the block.

What I did find, was that the motor apparently had been in salt water numerous times & had not been flushed well, if at all.  When I took the gasket off the head, there were salt crystals/aluminum corrosion pretty well blocking the lower cylinder's water jacket passage in the head.  This model has the thermostat at this lower location.  The water passages in the head were blocked solidly enough that I doubt that very little water could have even passed on into the completely plugged thermostat, much less on thru the rest of the engine & on out.  Pictures are shown below in "The Possible Water Circulation Problems" section below.

After I got the powerhead placed on my other 1974 motor that had a rusted crankshaft, I had problems keeping the motor running right.  Compression was 102 & 105.  I had put new aftermarket points & condensers in it among other things, but had problems that I eventually tracked down to mismatched flywheel & crankshaft tapers which kept shearing flywheel keys.  This motor would run OK on 2 cylinders, then down to one, then hard to start, & I was chasing my tail.  I finally took the timing plate & main ignition coil to a marine mechanic when I was in his locality to have the coil checked.  In order to check it he had to remove the screw holding the condenser to the points.  The ignition coil checked out OK, but he recommended that I purchase new points & condensers.    He said the points looked pretty bad.   BULL $HIT.  Well, I understand a shop wanting to replace anything that may have been a potential problem when they do a repair so that the job will not come back for a free repair later.  However I was doing the repairs & on these points, he could not see inside of the contacts without totally removing them from the timing plate & then taking them apart so he could really inspect them.   And being new, they probably only had an hours run time on them.   He must have better than my 20-15 vision.  I did buy the condensers from him, checked the grounds, repaired the flywheel taper, replaced the key & got it running.

Story #2 --  Another situation presented itself that bothers me, relates to dealer ethics.   I again purchased off eBay a 1987 15hp Johnson motor for $76 that was sold as "needing repair/for parts".  It was close enough to me (150 miles) so I took the wife for a drive & personally picked it up from the young man.  He advertised it as needing rings & that he had the marine shop's estimates.  He is a young Coast Guardsman & had gotten the motor from his father 2 years before but had never ran it.  On his first attempt ever to start it in the spring of 2005, it would not start, so he took it to a marine repair shop in a decent sized town located on salt water with lots of boat traffic, which should have had enough exposure to be pretty well acquainted with outboard motor problems, plus they did all the Coast Guard's repair work (why he took it there).  He had also broken the starter rope in his efforts, since he apparently was not aware that the motor needed to be in neutral when trying to start it.  The work order he gave me from the dealer says "low compression - pull head & diagnose, & call with estimate.  recoil repair".

The diagnosis reads "Bad Rings - new power head, not cost effective to repair unit".  They had taken the head off, inspected the piston & rings,  re-bolted the head back on lightly & without the gasket (apparently to prove they had it apart).   The headgasket, broken recoil starter rope & handle were stuffed under the motor's cowling.  The estimate of needed parts included carburetor kit, fuel kit, water pump kit, rings, rod bearings, wrist pin & bearings, main bearings & seals, oversize pistons & rebore to match pistons & a thermostat for a total parts estimate of $294.  This mind you did not include over $400 for the labor.

OK, on the surface this looks like it could be appropriate.  But after I got it home, I noticed on the top of the flywheel was written in felt pen, "Comp 1 -  100#,  2 - 105#, & spark OK".  I took the head back off & the pistons were clean, with no carbon, there was wear of about .010 of apparent piston wear.  Yes, it was WORN a lot as the pistons could be wobbled somewhat.  But my thoughts were if compression was at the 100#,  why did they even take the head off?   I just reassembled it using the original head gasket with some gasket sealant.  I had a used starter rope that I installed.  BUT -- the one thing I did install that was missing, was the "C" shaped horseshoe clip in the kill button on the end of the twist grip.

I had the motor running within 3 min.  My question is, how did they check the spark without using their own clip on the kill button.  And with the broken starter rope, they would have to have used a emergency starter rope to get the compression, which would not be an impossible thing.  It would appear that they never told the young man about the "kill override switch, otherwise known as man overboard switch" was missing.  OK, maybe this now running motor is not 100% factory new, but it ran for 2 fishing seasons for me as a normal fishing motor before it finally fouled the plugs so bad that it needed new pistons & rings. 

My guess is that this young man did not know anything about the "Man Overboard Kill Switch Lanyard" that was missing.  With this gone, it was essentially like turning off the key.  They could have replaced the starter rope, changed plugs, adjusted the carburetor idle & charged him $100 to $150, he would have been happy & they made a enough to cover the diagnosis & the actual repair to have also made a profit.   I will bet they even tried to sell him a newer motor & or offered him a minimal trade in.

Story #3 -- I happened to be talking to my neighbor & school mate when I spied an older 1960 10hp QD Johnson, I asked how it was running.  His response was, well it had belonged to his Dad many years before & had been setting for some time, & when his sons decided to use it, sad to say the water pump did not function.  They took it to an independent marine mechanic (well known to the locals as being a scalper), who replaced the water pump impeller for a mere $200.  They thought they got a good deal, as he told them that a new motor of that size would have cost them over $2000. 

 

This may not have been a proper comparison as he was referring to a new motor, but in any event the repair was still about 1/2 of the price of a current used motor of the same year.  This mechanic should have had less than an hour labor & possibly $20 worth of parts in this repair.  I have since had a chance to inspect his repair on this motor & it appears that he just installed a new impeller that is a simple repair, that I have done on this series motor in 15 minutes.  From the experiences I have had with this mechanic, he is one of those smart A$$es, looks at how you dress, the vehicle you drive, plays a sucker game & adjusts the price accordingly.   His cash register is his wallet & of course no receipt.

Just one more of the reasons why I am writing this article.

History of This Series:  Johnson was one division of OMC, (Outboard Motor Corp) while Evinrude was the other half.  This came about by the merger of both companies in the early 1956.  Both brands of motors then came from the same plant after that.  Evinrude was usually painted a blue color of some sorts, while Johnson was initially green until 1977 & then again white.  Late 1990's they both were either black, white or a blue gray depending on the year.   OMC filed for chapter 11 bankruptcy &  in October 2001, & Bombardier Corp. a Canadian manufacturer that builds snow mobiles plus a multitude of other vehicles bought the outboard motor division.

The earlier Johnson 10 hp QD series motors were made from 1949 thru 1963.   In 1958 these motors had a face change utilizing a newer style motor cowling & a change in color.   The 9.5 hp Johnson & Evinrude motors were made from 1964 to 1973.  These 9.5 hp motor's early model number was MQ up until the model code was changed incorporating the date in 1969.   If you need year of  a manufacture for these motors, or any before OMC went to the year code in 1977, as described below, go to http://www.marineengine.com/manuals/johnson/. 

 

Please excuse me for focusing on the Johnson brand, while after 1956 under the OMC manufacturer, both motors were made in the same plant, but painted a different color & sold to different dealers.  It is just simpler in these articles to focus on one manufacturer, and there appear to be more old Johnsons floating around than Evinrudes.

 

The 9.9 hp motors covered in this article, came into being in 1974.   As for actual physical differences between the 9.9 & the 15 hp that you could use for identification other than the decal markings, year by year these 2 hp sizes & brands are the same.  If the top cowling was removed & lost, the name/model plate was missing, then to tell the difference you may have to remove the carburetor & measure the inside throat to tell if it was a 9.9 or 15 hp. 

The Johnson line of 9.9 motors remained the same as far as calling it a 9.9 hp.   However Evinrude had a 10 hp designation on some of the later ones from about 1990 or so.   Same motor, but they apparently just changed the stated rating for advertising purposes.  The reason this motor was originally called a 9.9 hp, was at the time of it's inception, the US Coast Guard's terminology for registering a boat was that if it used a motor of less than a 10 hp & the boat was less than 16' long, it did not need to be licensed IF not used on Federal waters.  All 15 hp motors for both Johnson & Evinrude were called 15hp.

The piston diameter for both the 9.9 & 15 hp motors are 2.188" with a stroke length of 1.760"  which equals 13.2 cubic inches or 216 cubic centimeters.  Full power operating RPM for the 9.9 is 4500 - 5500.  The 15 hp motor is rated at 5500 -7000 RPM according to a 1978 Johnson sales brochure.
 
These were the second series of motors in this size range which were made with the compact lowered powerhead (the 9.5 being the first) & more easily fished over the top of & set the trend for other manufacturers to follow.  This series of motors appears to have been among the first of the thru the prop exhaust motors.  The outward appearance of this motor, other than paint & decals, remained virtually unchanged for 18 years, & even up until it ended in late 2006, it evolved into the backbone for the current 2 stroke model.  Both the current 2 stroke & 4 stroke motors use the same water pump & virtually the same lower unit (slight external changes) as the 1974 version.  OMC apparently learned something on the 9.5, as the 9.9 is basically a detuned 15 hp, initially using only a different carburetor & decals on the cowling. 

Observance :  It has been noted that since I have started these articles & have gotten many e-mails from all over the world that other country's motors may not be exact to what we see in the United States.  To me this means that if there could be an overage of production parts for a certain year, that the new model would be sold in the US, but the other countries could have been used as a cleanup of parts & you could see some differences as to electronics, decals, colors etc.  There could even be specials made to slightly different European specifications.  Or some specific things would be made available like the AC lighting for some European motors.  And possible at times the year models would be a year behind the ones sold in the US.

When a new design is brought out, it seems that there will surely be modifications needed to correct unforeseen defects or problems that do pop up.   However it seems when OMC came out with a new design or an "improvement" to the design that they are hesitant in making a quick change for 3 years.  This is evident in that the first models in 1974 used points & coils until 1976 when the electronics went to a Capacitor Discharge system.  The carburetor seem to be changed in either 3 or 6 year increments.  

It is suspected that possibly they want the design to run for long enough to really perfect a better part?   Or more than likely that they needed to keep those parts in production so that inventory restocking would not become a nightmare by being changed every year or so.   If they worked on a 3 year cycle it would not be as bad & a better parts interchange.                                                                 

 

Year of Manufacture :  This is important in any repair, for obvious reasons.  Prior to 1979, Johnson used the last 2 digits of the year in the model number.  As a model 10R78M, would indicate a 10 hp, Rope starter, 1978 year of manufacture & M model revision.  Since this does not have in the code L between the hp designation & the year, it is a short shaft version.   Evinrude in those years used a different 5 digit model code, as 10424S.  The numbers  you are looking for will be the first 3 numbers which equates to the hp & then the middle to the year, as 10 hp, the (4) equates to 1974 & the (S )would indicate a shorts shaft.  Here is a LINK to help you determine any of the Johnsons.  And here is the LINK for the Evinrudes.  For those of you readers outside of the United States, here is another LINK that may better help with your motors.

 

After 1979, OMC's manufacturing year code, which included Evinrude, is the word "INTRODUCES", with each letter equating to a number ie:  I=1, N=2, T=3, R=4, etc. as illustrated below.  As before, the last 3 letters are what you are looking for.  Then in this case, disregard the last one, as it pertains only to a model revision that only on specific cases may be revalent to a marine repairman if problems arise.  A code of  J10ELENA would equate to Johnson, 10hp, Electric start, Long 20" shaft, EN = 1992, & the A could be a model revision, so this motor would probably be made in the very first part of the year.  You may encounter a code of something similar to J10SELCTC. This would have been  Johnson, 10hp, SailMaster, Electric start, Extra Long shaft, 1983, & the C could be a model revision.  In this case with the SE in the model number, indicating a SailMaster, all the SailMasters would have all had the extra long 25" shaft.   For more detailed information on worldwide production, CLICK HERE

 

 

Using this code system, if the motor was sold as an Evinrude, then the first letter would have been an E instead of the J.   Then you can encounter motors made in or for other countries, which will have some added letters as mentioned later in this article.

Sometimes the nameplate found on the LH side of the upper steering/clamping bracket can get removed.  If this happens, you can still usually tell which motor it is by looking at the 25 cent size soft plug in the upper rear RH side of the block.  The model & year are stamped in this soft plug also but probably only up to 1979.  It is interesting to also note that the 15 hp uses the same block as the 9.9, so you could see a 15 hp with the same 10R78M numbers here as the 9.9 has.   I have heard from more than one person that their plug had numbers that do not match any of the codes, so this kind of backs up the idea of a change after the 1979 date, as the factory changed things as time went on.

 

If you need to check on parts & do not have a actual parts list booklet, one of your best sources is http://www.crowleymarine.com/   They have a complete listing of about all of the Johnson & Evinrude motors showing exploded parts views with part numbers & you can order parts online from them.  Or this one http://www.marineengine.com/parts/parts.html

In 1981 the marine industry went from powerhead rating to a prop rating.  The word was that the imported Japanese engines of the same rating were outperforming the US engines, as they were rated differently.  To get the equivalent prop HP on a US motor prior to 1981, take the HP rating & subtract about 10%, this will get you close to the newer rating.

 

One thing that I have found is that the pre 1977 motors which have the points & condensers seem to be a little cold blooded, in that they have to warm up before they will stay idling as for trolling.  Also do not knock these pre electronic ignition models.  Many boaters are not interested in these motors, preferring the electronic ignition, & I have to say if I had a choice I would also, but the older point system has performed quite well until modern technology came along.  They just require a little more prolonged maintenance.

 
Controls from 1974 to 1985:   This series of motors have all the same basic controls.  That is on the front panel, the choke pull knob is on the left side looking back to the motor.  To the immediate right is a large (approx 1" dia) knob that rotates, but will only go about 1 turn.  This is the carburetor idle adjustment knob.  In the center is the manual starter pull handle.  On the far right will be the kill button.  If it is electric start, on the left side looking from the front, hidden in the mounting base is the start button.

 

In Europe, at least from 1979 to 1983 manual start 9.9hp motors uses a lanyard man overboard kill cord BUT the clip is attached to a different secondary kill button which is located in the normal location as the electric starter button located in the US.  This lanyard clip, when pulled out kills the motor.  The regular kill button is still in place & functional however.  This same motor has the AC lighting plug on the port side like mentioned farther down in this article.
 

On the left side looking forward, is another large black knob located immediately behind the fuel line connector.  It is the idle speed control screw.  In effect this is basically for setting a trolling speed, where you want to return to after making a run without playing with the twist knob.  In setting this one, you may have to adjust it & the carburetor idle knob simultaneously to fine tune each.  This idle speed control knob is prone to abuse & the snap ring retainer groove can get broken which allows this knob & stop screw to become inoperable.  It is unique in that the threads are LH.  

One cure for it without purchasing a new knob is to do some measuring & eliminate the wafer washer under the snap ring.  Put the knob in a metal lathe & carefully move the shank back into the knob area, deducting the .050 of the washer & recut the snap ring grove.  Shown below are the important dimensions.  The purple lines are what was removed.

 

 

On the right side again looking forward is the shift lever.  These shifting levers will be evident in the pictures listed under "Ignition".  Below the shift lever but just above the mounting brackets is a lever that moves forward & back.   It locks the motor down so that if you put it in reverse & try to attain a high speed, that the lower unit will not jump up & out of the water.  This lever, when moved forward, allows you to raise the motor & lock it in the up/out of the water position.  Also in the same 2 bottom pictures referred to above, you will see the black lever described just previously. The upper cowling lever is located at the rear & under the edge of the cowling, rotating it down allows you to remove the upper cowling to access the engine compartment.

 

Controls from 1986 to 1992:   Apparently in late 1985 a change was made to the tiller handle/throttle twist grip, I call this the type 2.   This cable system replaced the gear throttle linkage improving the situation dramatically.   At this time they also moved the kill button to the end of the tiller handle.  It has the word STOP on the end.   In 1987 they added the lanyard type kill button on the end of the twist throttle handle  These created a problem if you used the extended universal joint tiller handle, as you could not reach the kill button with this extended handle installed.  

 

In 1991 the handle was changed slightly & the kill button was moved to about mid handle left side.    These buttons for both type 3 & 4 also incorporated a man overboard kill switch.  The motor comes with a red coiled plastic cord that is attached to a split plastic section that is inserted UNDER this kill button.  The other end of the cord is to be attached to the operators wrist, so that in the event he falls overboard, this insert is pulled out & the spring loaded red button goes deeper in the housing just like turning a switch off (product liability).   In use this electrical circuit is just reversed from what most of us think, as with the clip inserted, turning the switch on, you are actually breaking any electrical connection.  To kill it by either the clip missing or by you pushing the button, you ground out the wiring, killing the motor.

 

In use, this red button HAS to have either the lanyard insert clip under the button, (turning the ignition ON) or a another smaller that one called a "restart clip" shown below on the 2 photos on the right, that is inserted instead of the lanyard if the owner decides he does not want the lanyard safety device.

 

On type 2, 3 & 4 the ribbed plastic end plug is made to rotate.  This is to fine tune adjust the idle for trolling, as these motors do not have the LH side trolling adjustment knob.  In the photo for type 3 you will see a black "U" shaped clip  attached to the top base of the handle.  This is spare that was original equipment.  Another like it had the red coiled plastic looped cable with a clip to attach to the operators arm.  In the RH photo you will notice a lighter red colored "U" clip under the end button.  The angle of the photo for type 3 does not show this clip well.  This is the restart clip as described below.

 

The type 1 twist grip may have different grips depending on the vintage of the motor, the early ones being a white plastic.  The electric starter button remains in the same position on the LH side in the mount clamping area for all these motors as the previous versions up thru 1992.

 

As shown above, on motors made from 1987 & on which have the kill button on the tiller handle, if either of the clips shown below are missing the motor will not start, kind of like turning a key OFF.   There are 2 variations of this, the one shown is from a 1987 to about 1990, which as it on the end of the twist grip throttle handle.  After that, the clip was moved to a separate switch about 1/2 way up the handle, while retaining the smaller twist knob as a slow speed limit control.

The above the following information are a reprint of OMC installation instructions for "OMC Clip Assembly P/N 431808" dated 3/87.  This part is also known in the parts manual as (Restart Clip).  "This clip assembly is for use, under limited conditions, on models with an Emergency Ignition Cut-Off  Switch located in the steering handle.  Make sure that you are aware of the purpose and benefits of the Emergency Ignition Cut-Off  Switch  as described in your Owner's /Operator's Manual before disabling.

Outboard motors used in certain applications, e.g. auxiliary power on cruising sailboats or as a trolling motor on larger fishing rigs, may NOT be able to take advantage of the benefits  provided by the Emergency Ignition Cut-Off  Switch feature.  For applications such as these, the cut-off switch can be disabled by replacing the clip and lanyard assembly (A) with the OMC Clip Assembly (B), as shown.  The clip (B) will disable the cut-off switch while retaining the "PUSH" Stop Button feature.  If the motor application changes, reactivate the cut-off switch feature by replacing the clip (B) with the original clip and lanyard assembly (A)".

The Type 2 thru Type 4 made from late 1986 to 1992 use a cable system for the throttle advance (as shown below) instead of the old troublesome gears system.  The rear end of the cable is threaded for adjustment to the plastic coupler that snaps over the steel ball on the pivoting connector that is in turn pinned to the timing plate arm.  This threaded end can give some final adjustment in addition to the twist grip plastic end cap adjustment for slow speed idling.

 

How to Start Your Motor :  I get inquiries at times & some owners do not know or understand the basics of starting an outboard motor, so. The first series in 1974 had a nameplate riveted onto the bracket just below the control panel, stating:   "Starting Instructions:  Read owners manual.  Connect fuel line to motor.  Squeeze primer bulb unit pressure is felt.  Shift to neutral.  Twist grip to start position.  Pull choke knob out.  Pull starter handle.  Push in choke knob as engine warms up.  Stop button on control panel.  Spark plug UL4J.  OMC  sea-lube gearcase lubricant."

 

Now one thing to remember is that usually the throttle labels on the tiller are very vague and are more a reference point than actual throttle position.   This said, a motor will start if the actual position is a little faster, BUT may not even sputter if set to slow.  However when shifting always try to be as low as possible to help alleviate a lot of gear grinding.

Engine Has Sat For a While :  If the engine hasn't been used in quite awhile, very possibly with gas sitting in the carburetor, it may possibly require cleaning, which seems to be the standard recommendation for motors in this situation.  However, it may be worthwhile to try to run it at least once before jumping into a carburetor repair.  I have found that sometimes the gasket between the main carburetor body & the bottom fuel bowl can deteriorate.  When this happens, for what ever reason, chunks of the neoprene gasket get into the fuel bowl & can partially plug the high speed jet, cause erratic engine performance.  It has also been found that the newer non-leaded gasoline is less likely to cause internal gumming problems in the carburetor if allowed to set for extended periods of time.

The only way to fix a clogged/fouled carburetor is to remove, dismantle, clean, and rebuild it.  Do not try to spray a carburetor cleaner in the breather or run it thru the fuel & expect it to do a cleaning job.  If you try this while the engine is running it very well could ruin the engine, as there would be little lubricant inside the engine for the bearings.  If you take the carburetor apart, make notes and drawings as to what goes where, or use a digital camera.  Regardless of how simple it seems, you will find something where you can't remember how it should be when it comes time to put the parts back together.

 

The One Weak Thing on This Motor :  The first series (that I designate as type 1) up to & including 1985 uses twist grip gear teeth to activate the throttle on this series.  As described above these gear teeth  mesh on both the twist shaft & the mating  linkage shaft gear function so that the handle can be raised & lowered & yet be twisted.  BUT this feature was not really intended to be used this way as mentioned earlier under "Remote Controls".   DO NOT RAISE the handle very high & twist the throttle unless you are prepared to disengage the gears, & change the twist grip timing relationship.  This is explained in a subsequent section.  Pictures show this relationship in the Trouble Shooting section.   Later, in about 1986 a throttle cable push/pull system was used to eliminate this problem.

 

Difference between the 9.9 & 15hp : When they designed this series of motors, they designed it as a 15 hp & then detuned it with a different carburetor for the 9.9.   When the 9.9hp and 15hp came into being in 1974 and up thru 1978, the only real difference between the two motors was the carburetor.  In 1979 they added a shim, part #325038, (one for each cylinder), behind the leaf valves & under the stop plate for the 15 hp, apparently to allow the motor to suck more fuel & air mixture in.  

 

It is my experience that the 15 hp does not idle down as slow as the 9.9 does.  It should not really make that much difference as at an idle they use a different idle jet than the main jet, except that the 15 has a larger throat size & apparently needs slightly more fuel even at an idle (trolling speed).  So if you intend to troll for trout at a SLOW speed, stay with the 9.9 carburetor, however if you want it for a backup motor & salmon troller then consider the 15 hp.

 

The outside visual dimensions of both carburetors appear the same, unless you look inside the throat.  If you look in from the rear, you will have to position the throttle plate to a horizontal position to be able to see the throat very well.   The 9.9 hp carburetor’s INTERNAL THROAT is .625 dia., 15 hp internal throat is .875 dia. up until late 1987 when they went to a plastic topped carburetor.    NOTE this is not measured from either the from or back but the internal throat that you can see on the LH photo below.   The outlet or rear throat dia. is the same on both to match the manifold port dia.   The idle jet venturi system is also slightly different between the two.  The part number for the the pre 1987  9.9 hp Carburetor Assembly  is #388936, while the 15 hp Carburetor Assembly is #338273.   This increased throat dia. & larger main jet allowed it to breather better & pull more fuel in, increasing the RPM about 1000 RPM, hence more HP.  

 

 

A problem in buying a used carburetor is that the part number may be hard to read as it is only stenciled on.   And many people, even marine mechanics, do not see enough of these to be really sure which is which unless they see them side by side.   The reason for this is that when these motors were sold new, say in 1978 the 9.9 went for $647.75, while the 15hp was another $150.   Needless to say way more 9.9's were sold than the 15's by possibly 80%, therefore considerably less used 15's parts are available.

 

In 1981 there was a change made in the inner exhaust housing for the 15 hp OMCs only.  It was a sort of tuned round exhaust housing, allowing the engine to again breathe better, which  in addition to the larger throated carburetor, & the leaf valve shim gained about another 10%  in overall HP to put these OMC engines on par with the Japanese imports.  The 9.9 hp square inner exhaust housing & no shim for the leaf valve, stayed the same as it was.  The big difference in the performance between the 9.9 & 15 hp will be in the last 1/3 of the throttle range where the increased fuel/air flow of the carburetor will be readily apparent with the increase in RPM.  

 

In the photos below, the early 9.9 & 15 hp exhaust housings are on the far left with the tuned 15 hp on the right in both photos.

 

Later motors, at about 1990 the 9.9hp uses the 15hp exhaust housing.  
 

You will note that there were 3 different ongoing 15 hp modifications.   (1) The 15 hp from 1974 to early 1987, with just the different metal topped carburetor.  (2) The added leaf valve shim in 1979.  (3) And the added tuned exhaust system in  1981, which also included the 2 previous modifications.  The 1979 parts manual lists a shim, part #325038 to go between the leaf valve & the stop for the 15 hp only.  This shim sells for $2.94 each.  It is carried on up into 1992 for the 15 hp, which apparently allows the 15 hp to breathe a little better.   These leaf valves are the same for all motors they are used on.

 

Now before you run out & find 15 hp parts to convert your 9.9, here are some drawbacks.  I have 2 friends that have these 15 hp motors & both essentially for trolling.  The problem that both encounter is that they foul spark plugs more regularly than if the motor was a 9.9.  I suspect that could be from 2 situations.  (1) Here both say they are using 50-1 oil mix.  This is combination recommended, but you will notice in this article that I have experimented with the ratio & oil type & have found what I consider a better combination.  My combination would extend their run time before changing plugs, how much I an not sure.  (2) Since the carburetor has a larger throat, the idle jet would have to allow more fuel into the engine to give the proper fuel to air mix otherwise the engine would be running lean.  With this enriched idle mixture, this would explain the more frequent plug fouling.

 

Special Motors :  Sometimes odd-ball motors pop out of the woodwork.  Here is an interesting bit of information, for a Johnson "GT10" which is actually a "restricted" 15hp motor, & not a true 9.9hp.   It is actually a 15hp motor with a 15hp carburetor but with a restrictor plate between the carburetor & the intake manifold apparently to economically reduce power to 10hp.   This apparently was introduced to modify an existing 15hp to get round legislation for the amount of HP on certain waterways.   Why not just sell a 9.9, unless there were more 15hp motors in inventory & this was a quick way to dispose of them.

The model number is BJ10SPCEC, which places it as a 1989.  This one is from Europe, made in Belgium, short shaft, electric start & with an AC lighting outlet.   I would think trying to troll with a motor modified in this manner may not be ideal even though the carburetor would be adjusted downward to any possible idle smoothness matching the air flow.  But it was a motor designed by engineers to meet a political issue, so what the heck.
 

 

Hard Starting : These motors are hard to start unless the choke is staying fully closed while starting.  Verify that the stainless steel tang that holds the plastic choke lever in place is doing its job, after a while they need to be re-bent back in place to apply enough tension on that choke rod notch to hold the choke in position.  Also verify that you have replaced the choke knob right.   If your choke knob shaft was installed upside down, the choke butterfly will not completely close, thereby not being able to choke the engine when doing  a cold start. The wider slot on choke knob shaft (the connection point to choke butterfly lever) goes up.
 

Carburetor, Early :  Do not think that you can up the horsepower by simply modifying a existing 9.9 carburetor by replacing the main jet with a 15hp main jet.   All you accomplish is that the engine is being fed too much fuel & not enough air to properly mix with it & the engine will then blubber (floods out) at the top end.   It can run OK on the lower end & idle OK because it is using the idle jet then, but it will have less top end power than with the original 9.9 main-jet.   Believe me, as I have been there/done that.  Matter of fact that is what years ago got me into writing the original of this article so I could document & remember myself, as I could not readily find any factual information on the subject, only speculation.  To reiterate the above, a 15 hp main jet modified 9.9 carburetor WILL NOT work.

Early production motors had all metal carburetors.  Then from about 1980 to late 1987 the same basic carburetor as previously was used, but had a black plastic bottom fuel bowl.  This plastic seemed to be an improvement in that if water had entered in the system & got in the bowel, then sat for a while creating RUST inside the carburetor & even enough rust on the outside if used near saltwater to corrode holes in it.  For a more complete information on the carburetors of these motors CLICK HERE.

 

Carburetor, Late : Late 1987 & newer production carburetors up thru 1992 were completely different & had the bottom fuel bowl & top made of heavy black plastic type material.  The choke lever is the same in these newer carburetors even though the motors used the cable twist grip which utilized a totally different throttle system.

 

They were apparently designed for easier manufacture as the plastic top has the idle jet in it & the juncture between this top & the main body serves as a passage (depending on the the gasket) for the fuel from one chamber to the other. 

 

The choke butterfly is the same as the previous models, but the throttle plate is smaller.  The internal throat of the 9.9 is about .500 dia. while the outlet hole into the manifold is .750 dia.  
 

If you see a carburetor advertised on e-Bay that does not have the above RH side choke lever, but only a shaft protruding with a roll pin installed, it will be for a 1993 or later motor, as the choke lever is different for these.

 

There then was another twist that you may encounter & that is a remote controlled motor that has a electric choke.  On these there is a small solenoid with a wire running up to the choke lever on the carburetor for activation when you push the remote choke button.

 

Update Carburetor Top Cover:  The new style black plastic topped carburetors used on motors made from late 1987 to 1992 had a habit of the plastic top warping or cracking.  The crack begins near the front hole for the idle needle jet & running along the top of the cover over the needle cavity.  Warping occurs at the middle rear.  Either could allow air into the idle circuit making for a rough running motor. 

The factory came up with a reinforced top cover to rectify this situation.  The fuel circuit on the new cover is different from the older cover & the gasket that fits between the cover and body is also different.  This new cover used the same number of screws as the old cover did. 

From what I can find out the older covers can be identified by the pivot for the throttle cam roller with this pivot being a metal screw that screws into the top cover.  The later update covers utilize the pivot shaft as integral with the plastic top & use a O-Ring as a retainer for the roller arm. 

 

The 1993 and newer carburetors again changed the design using 6 cover screws instead of the 5 used on the 87-92 carburetors.

 

The part numbers in the replacement parts & prices as of 2007 are as follows:

 

Carburetor body cover #337833    $8.50

Cover gasket #334043                   $3.75

Or they would be included in carburetor repair kit #439073   $34.00

 

The repair kit lists as being for, 10/14 hp  87-91, 10/15 hp Commercial models – 92.   And 9.9/15 hp recreational models 87-92 using carburetor with separate black cover (original part # 331735 or 334050)

 

Removal of the Carburetor :  You need to remove the plastic carburetor intake cover (OMC calls it a silencer).   However the early ones I have seen are white instead of the common black color that is on the later versions.  It just could have been that some  motors that had white ones that were made of a material that did not survive vibrations as I have seen may missing.  Remove the choke lever & the idle knob.  When removing the idle knob, make note as to the location where the indicator tit is pointing, as you should replace it in the same location when reassembling.

 

You also need to remove the recoil starter unit.  The manual starter unit can be unbolted with the one 9/16” headed bolt head in the center of the recoil unit.  Be very careful as that spring is dangerous!  Pull the rope out a few feet and tie a slip knot in it so that it can't rewind back.  Carefully remove the starter handle, then grab the rope inside at the starter pulley, then let the rope withdraw somewhat but not completely (leave a foot or so to work with).  Now, secure the rope inside at the starter pulley to the upright pulley gear guide in a manner that will prevent the spring from rewinding the cord etc.  Hold the manual starter assembly together when loosening the top large retaining bolt (do not remove that bolt completely from the starter housing assembly).  Carefully remove the starter assembly while holding it together.  Screw a 3/8" nut on the bottom of that large retaining bolt to hold the starter together while you're working on other components.   

 

There is a small coil spring (#1 in the photo below) from the carburetor to the ratchet of the starter & up to about 1979 that needs to be unhooked.  This spring's tension is released by a lug that the timing plate cam positions when the twist grip & shifting lever are in neutral.  If the throttle is faster & the motor is in gear this black plastic dog drops down into the starter spool teeth, not allowing the manual starter to be pulled.   This dog's function will still operate by gravity if the spring #320490 is missing, but not as positively.  This spring is obsolete & only available from aftermarket suppliers at a cost of $9.95.

 

There is also a Z link rod (#2 below) This ties the roller bar unit to the throttle valve of the carburetor.  Do not loose it either, or a makeshift one will need to be fashioned as this #2 is below from a piece of welding rod.  The important thing here is to get the bends just right so that the timing is consistent  when the timing plate moves this roller forward to give movement in the throttle valve increasing fuel flow.
  

 

Now you can get to the RH (looking forward) carburetor nut more easily.  The LH nut is harder to get to & you may only get the nut to move one flat at a time with the wrench.  You may also decide that by removing the flywheel it is easier to get to this LH nut.

 

Shown below is a modified 3/8" combination wrench that has been opened up to 7/16"  & relief cuts made on the sides specifically for use on these carburetors.   Removal can be done with regular 7/16" wrenches, but is cumbersome.  The reason for using the 3/8" wrench was that it being smaller, required less relief cuts to be made.

 

 

Clean & Rebuild the Carburetor :  Remove the fuel line.  Disassemble the unit.  Once the carburetor is off, unscrew the bottom screws that hold the sheet-metal bottom pan on.  When removing this pan, be careful & try to save the gasket if you are not going to get a repair kit.  Remove the cross pin that holds the float, remove the float & the needle valve.  You will need to also remove the idle shaft screw, count the revolutions it takes before it comes out.  In this way you can replace it with the same number of revolutions when you reassemble it.  Normal screw setting of this (lean/rich) idle screw will be starting at 1 1/2 turns out from lightly bottomed out.

 

If the insides are dirty, you can get a can of carburetor cleaner & spray on or soak until things soften up.  Usually you can use an air hose to blow thru the passages & be sure they are clear.

 

The older floats are made of varnished cork & can get deteriorated over time & may not function properly, if so replace it with the newer black plastic type.
 

In rebuilding your carburetor using a kit; make sure you remove welch plug (a small 1/4" dia. aluminum plug) on top of carburetor and get the idle circuit holes absolutely clean and blown out with compressed air.  This plug can be removed using a ice pick.  You will ruin it, but try not to damage the carburetor body as the new plug needs to seat airtight.  I have even used the old plug, by tapping it back in place & JB Welding the ice-pick hole up.

 

Dies When You Put it in Reverse:   If the idle speed is too low, it will stall when you put it in reverse from an idle.  It takes very little power to run in neutral.  It takes more power to run in reverse, (because of the propeller now running backwards) so if it is idling too slow, reverse is the gear that will cause it to stall as compared to going into forward.  

If the idle speed in a test barrel if set correctly, 675-750 RPM in forward gear, you will probably see something like 800-900 in neutral, and 600 in reverse.  But if it is set it for 600 in forward and then reverse will drag it down to around 500 which is to slow to run.

 

Removal of Intake Manifold :  It is very unlikely that you need to do this, but just in case here are some pointers.  It is just about as easy to remove the powerhead from the midsection as try to just remove the manifold.  The bottom 1/4" bolts are a tight location to access.  While the carburetor is off, you will need a 1/4" drive speed handle & preferably a 7/16" wobbly socket, (one that is a combo universal joint & socket combined). You may be able to squeak by with a universal & a thin socket after taking out the front motor mount screw, which will allow you to gain a slight amount of room.  The hard ones are the RH & LH bottom, as the RH bolt is tucked under the support bracket.  The LH one you will have to remove the bolts from the shifter shaft & slide it to the left enough to get the socket on the bolt head.  On motors made in the first 2-3 years of this model, I have found that these bolts are indeed a 1/4" course thread, but using a head size of 3/8"

 

You may be able to twist the manifold enough to get it up & out from under the throttle cam plate.  But in reassembling when you have the gasket in place, it may well be best to remove the stator & timing plate.  In doing this you now can position the manifold & gasket in the proper place without disturbing the gaskets location.  Otherwise you may be taking it off again, as there is a fuel drain hole in the bottom of the manifold that allows excess fuel to drain back into the crankcase, that if not sealed good with the gasket, will allow gasoline to dribble out & down along side the block & upper housing.  

 

Check the leaf valves, (commonly called reed valves) or replace them.  When reinstalling or replacing these reed valves be sure that you position them so that they are centered over the holes so no leakage can occur.  Clean the old gasket & use a good gasoline resistant sealant on the new gaskets & reassemble in reverse order.   Be sure if you use new gaskets that you use the right ones, it uses 2 different ones with slightly different small holes on one.   Also be sure that you install these gaskets on the proper sides of the valve plate.  If you get them mixed up, the wrong one has a smaller size opening on at the reed valve area & WILL restrict the valve movement to where the motor will not be getting any fuel into the motor itself.  

 

Reinstall & Adjust the Carburetor :  After reinstalling the carburetor to the intake housing & you need to reinstalled the choke pull knob.  The choke knob shaft has a slot in the middle that the carburetor's choke lever goes into.  This shaft needs to be installed with the longest length of the slot upwards, otherwise the choke lever does not have enough room to function.  Now you need to re-install the plastic carburetor intake cover.  The idle knob is next.  Even after you replace in the same location as it was before tearing it down, & you get it running again, you may need to fine-tune adjust this idle knob for trolling.

 

There is also a large knob on the left hand side of the lower cowling on all but the very early years motors.  This large knob activates an internal threaded rod that acts as a stop for the throttle plate linkage & is used for a slow speed setting, (not to be confused with the actual carburetor idle settings).  After 1987 this knob was discontinued when the cable throttle system was instituted.  The new slow speed setting was then changed to a twist knob on the end of the twist throttle.

 

After the motor has been run enough to have it warmed up, try to let it idle.  If it runs to fast or slow you can adjust the large knob stop screw on the motors left hand side.  It may be best to initially do this with the motor cover off, so that you get an idea of which way to turn this screw.  Turning this knob counter-clockwise pulls the threaded rod out & makes the motor run slower.  

 

When you get the motor running near your trolling speed, then turn the carburetor idle knob  (lean/rich) clockwise a slight amount, let the motor run for a few minutes, & rotate it slightly more in the same direction again.  Doing this you are making the motor run leaner.  Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting & the smoothest the motor will run at slow speed. 

 

It make sense when shutting down the motor for what may well be a extended period of time, to disconnect the fuel line & run the motor unit it dies, using up all the fuel in the carburetor.

 

Hard Starting When Cold :  The one most common problem with hard cold starting, if the motor is in reasonably good running condition, can probably be contributed to someone who uses the motor strictly for lake trolling & is prone to adjust the idle jet lower than it is actually designed for.  When you are adjusting this timing & idle jet for slow trolling, you will be doing so while the motor is warm & running.  Then when the motor cools down, things are going to be slightly different.  What happens then is that in the cold starting mode, the motor does not get enough fuel, & you have to choke it & pull more times on the starter rope to get enough fuel into the cylinders for it to fire. 

 

One thing you may do in this case is to after you have adjusted it for your trolling speed is to then pull the knob straight forward & off the carburetor idle shaft, reposition the idle knob to position the pointer straight down & push it back on.  Then when you go to start it, you twist this knob counterclockwise all the way up (about 90 degrees) till it bumps.  This should give you more fuel to start, & then you can reset it back to your known trolling position later.

 

Another problem could be leaky reed valves at the reed valve base.  This could allow some of the intake fuel to be pushed back out on a firing cycle.

 

Another possibility is that the engine may have worn/leaking crankshaft seals.  This condition will not allow sufficient vacuum on the intake stroke to pull fuel from & thru the carburetor.  This is usually the top seal that is bad.  Some mechanics will tell you that it is the bottom crankshaft seal, I say not really as the lower one will not have as much side pressure on it as the top seal being near the rotating flywheel as the top bearing may also be worn.  It will usually make a mess under the flywheel, namely fuel/oil mix spilling down around the block.  My simple method of doing a check out of the top seal leaking is to pour a small amount of STP around the shaft/seal juncture.  It sure can't hurt anything & just may give you an indication as to if that is the problem.

 

Recently while talking to a couple of duck hunters who experienced a OMC 15 hp  THAT REFUSED TO START in freezing weather.  They mentioned that one COLD morning, they were not able to go out to the hunting grounds because of the non-starting motor & they were on a trip a considerable distance from home.  A trip of "let your fingers do the walking" thru the phone book took them to a old outboard mechanic that was operating out of his home shop.  When they explained the problem, he said OK I know what it is.  When they looked him up, he retrieved a propane torch & heated the spark plugs.  After reinstalling them, BINGO, the motor started.  His explanation was that on some of these older motors the compression may be lower during the cold weather & that there just is not enough compression to fire the fuel at the plugs with them being that cold. 

 

Motor Not Revving Up Like it Used To :  If all other normal things have been checked out & the motor will not run at the faster speed, sometimes if it has sat for some time with the fuel not run out of the carburetor when it was put away, the main jet can get partially plugged.  The bowl of the carburetor can also accumulate some debris.  If this happens, the motor may start & run at a medium speed, but is not getting enough fuel to allow it to run at a faster speed. 

 

The other thing is as mentioned previously that the twist throttle gears may be out of mesh.

 

Also if the timing plate linkage may have become disconnected from the upper throttle linkage peg, the motor will not run right.  This peg has a plastic bushing & wavy washer with a small cotter pin holding it all together.

 

Timing :  The throttle cam plate that rotates under the flywheel when you twist the twist grip & the plate has an raised line type mark on the front of it.  This mark needs to be timed so that when you advance the throttle twist grip, that the carburetor roller is at this mark when the carburetor throttle shaft just STARTS to turn open .  To adjust this on the older motors, you loosen the 2 bolts on the RH side of the plate & adjust the cam plate to where it just aligns with the roller at the same exact time that the throttle plate begins to rotate.   CLICK HERE for a link to the carburetor/fuel pump section for more detailed information.

 

If you are having problems locating a start position on your twist grip throttle setting, or if you have a remote throttle, a method of locating the timing "START" position would be to advance the timing plate to where the carburetor arm roller just touches the timing plate cam, then advance it about 3/8" (9-10mm) more.  This positions the timing & throttle at about the start position in the carburetor.

 

Pre 1977 Upgrade Kit:  Again this info was supplied by a reader that purchased a kit off e-Bay .  The info from that site reads.   "New Carburetion Improvement Kit part# 387256 for Johnson/Evinrude outboard 15 HP.   There is not a lot of information on these kits but these motors were afflicted with a lot of idle, stalling problems & fouling of spark plugs.  The kit has a new cylinder head, new carburetor, arced throttle cam and all the gaskets and spark plugs."

 

One reader who apparently was a mechanic at that time e-mailed me.  Here is his comments   "In 1974 OMC put out a service bulletin, and "recalled" all 15 H.P. engines for that model year.  If you recall there was a gas shortage that fall.   The problem was simply put....bad gas, or at least fuel that was too low in octane, to run the "higher compression" 15 H.P.   So each dealer was shipper a kit for each motor sold....... It was the kit in your picture, and was in fact the head off a 9.9 HP model, with a different throttle cam. etc.   Owners were notified to return the motor for an "upgrade"  which for all intensive purposes was to turn them into 9.9's.  Some dealers used the kits on stock motors, and others didn't they just put them on the shelves.   A few customers motors were actually converted.   I think if you measure the head carefully you will note it's lower compression.  I just thought I'd shed a little, I was there and done that!   Richard C. Wilson". 

 

I can find no data in any of the parts lists to substantiate the above "higher compression for the 15hp", but can surmise that the different carburetor in the mentioned kit was indeed a 9.9.  My reasoning is that if the fuel was indeed that bad, any extra supplied by the 15 carburetor would basically flood out or foul the plugs if trolled for any length of time.

 

What I have found is that the head was changed slightly internally to give better fuel flow at low RPM & as shown in the photo below identifiable by the scalloped out recesses for the spark plugs representing the heads found on the later 1977 & later heads.   From a old time mechanic that was doing warranty at that time, "If you examine the design of those powerheads, the fuel/air mix enters one side, is deflected up toward the head by the piston crown, then across the head and back down toward the exhaust ports.  Just like any crossflow 2 stroke.   However on the 9.9 and 15, the spark plugs are at a sharp angle, facing the fuel flow across the head.   So if the fuel is not completely vaporized, any liquid gas splattering against the head runs right into the spark plug.  The redesigned head has little dams around the spark plug to try to prevent that.   It helped, but certainly didn't cure the problem".   I have not been able to pinpoint why the need for a different timing plate cam however.   It does make sense that bad fuel could have been one component of the problem.   But with the lower output of the straight magneto setup with points and condensers, the spark plugs could very well become fouled, especially at a trolling speed.

 

 

One of the frequent contributors on i-boats.com forum has come up with another twist to help these pre 1977 motors out.   "I have also found "synching" the spark plugs helps too.   Orient the ground electrode towards the intake ports when you torque the plugs, the tip of the ground electrode will then face the exhaust ports (RH side looking forward). This then allows the ground electrode to shield the tip of the plug from raw fuel mist and prevent fouling and gives great low speed trolling.  I use a felt tip Sharpie pen to mark the plug so I can see where to stop tightening it such that it is aligned as described above, and repeat for the other plug.  Sometimes, you need to swap plugs to get them to line up at the right point when tightening, it's a trial and error thing.  I share this with you because it has really helped my fishing, as I troll a lot.  This synch trick came to me via 2-stroke motorcycle and Go Kart racers who I hang out with.... it works."  This is also how the new Evinrude E-Tec motor spark plugs are "Timed". 
 

From what is shown in the photo below, I will make some observations.   The head is a post 1977 as evidenced by the scalloped recesses for the spark plugs & a different color possibly for identification purposes of this kit.   The spark plugs may be a hotter heat range.  The carburetor is probably just a 9.9 as if the 15 hp motors that this was targeted for may have been getting more of the bad fuel (because of a larger main-jet) than they could handle at a trolling speed.  And I doubt the head gasket was a little thicker, just a requirement for proper head replacment.

 

 

Manual Starter Anchor Bolt Threads Becoming Stripped :  If this happens the threads in the aluminum base plate are what is stripped.  The manual starter will become floppy & may have problems engaging the flywheel ring gear.  If used extensively in this condition, the plastic starter spool gears will get chewed up.  The only practical way to cure this other than replace the manifold, is to drill out the base hole & tap it to install a Heli-Coil insert thread back to the original 3/8" NC thread.

 

Replacing the Manual Starter Rope or Spring :  The easiest way to replace the rope is to take the handle off, let the rope go to release spring tension and remove the recoil starter from the engine.  You can then remove the pulley and replace the rope.  On this recoil starter, the rope pulley is in two pieces held together with screws.   Watch how it comes apart and you should have not problem.   Re-wind the new rope (counter-clock wise) and re-install the starter.   Take a turn or two around the pulley with the rope to tighten up the spring a little and run the rope back out the rope hole and attach the handle.

If you are just replacing the rope, use a little caution when you pull the pulley free of the rewind spring.   They stick sometimes and can pull the spring out.   You don't want the spring to come out of the lower metal housing, otherwise it is a messy & tedious job rewinding the spring back into the housing.   Which brings us to replacing the spring, take the old one out, but be careful in that if it uncoils from the housing it can be dangerous, like a snake whipping around.  in replacing a new spring, they are encapsulated by a metal clip.   Some of them come with a metal clip retainer holding the spring wound up tightly.  Others the coil will not be wound as tight as needed to be placed inside the cup unit.  If the tight one, you are in luck, place the new spring in the old housing, & then take off the clip.   Rewind the rope & reassemble as described above.

 

If you need to rewind the old spring, or replace the large wound coil.  My experience is best to start it into the cup base with the outer looped end sticking out the slot.  Then wind the spring inside of itself, being very careful to hold things tight as you wind each successive coil inside the others.  Once you get the whole spring encapsulated, you can take a brief breath.  Now you can wind the rope back onto the spool & locate the spool's inner peg into the eye of the spring.

 

 

Reinstalling the Manual Starter Spool :  New rope is 5/32" dia & 72" long. The spool has to be replaced in the proper location.  The underside of this spool housing has a 90 degree metal lug protrusion that hangs down & goes into a round hole in the base that the unit bolts onto.  It is hard to see where this protrusion goes unless you place a felt pencil mark on the housing in line with this metal protrusion.  There is a flat washer between the mounting housing & the starter spool & under the recoil spring.  Be sure this washer is in this position, if you put it below the housing & above the bracket, the housing will compress the unit to the point it will bind & the spool will not rewind freely. 

 

The manual starter spool assembly was changed after 1978.  The rewind spring was changed in that the inner end of the early springs had a sharp bend back end to attach to the spool, which proved a weak point & would break.   In 1979 & later they added a separate starter spring retainer which linked between the spring & the spool.  At the same time the neutral safety interlock system & ratchet teeth were moved from the top to the side of the spool.    

 

You need to have the anchor bolt backed almost all the way out of the housing (but not all the way, otherwise the coiled spring may pop out of its housing) when you place the unit in position.  If when you get the spool unit in place & the metal protrusion in the hole, but have problems aligning the bolt into the hole, hold the unit together as best you can & you can remove the bolt.  Now you can look down thru the bolt hole & align the hole in the housing to the threaded hole in the base.  The flat washer needs to be installed under the anchor bolt's head, otherwise the starter gear will not stop on it's upward motion & bind in the flywheel gear teeth.

 

You will find it harder to get the manual starter out & back into position if you are working on an electric start version, as this ring gear makes for a closer fit.                                                                    

 

Removing the Flywheel:  If you have to remove the flywheel, you will first loosen the nut on top with a 7/8”socket wrench.  Unscrew this nut 3 or 4 complete turns so that it is even with the top of the crankshaft.  You can usually remove this flywheel by lifting upward on the flywheel putting upward pressure, (even if it is mounted on a rack or boat transom) & sharply rapping the nut with a decent sized brass or lead head hammer so you do not damage the threads or the nut. 

However of that fails, then you will have to use the 3 armed gear puller & the 3 holes in the top of the flywheel like it was designed to do.  Inspect the flywheel key for sloppiness or evidence that it does not fit snuggly, as this can allow the flywheel to move slightly & change the ignition timing.  Note, there is no lock washer under the nut here.  Be sure to replace the key in the crankshaft slot when you replace the flywheel.  The mating surfaces of the crankshaft taper & flywheel taper should be clean of debris & with no oil.

 

If you are forgetful or the tom cat's late night haunts might be hiding the flywheel nut on you, a replacement is 9/16" x 18 TPI or National Fine.

 

Flywheel Problems On Early Motors:  This applies only to the 1974-1976 magneto ignition motors.    We have here a situation where the point breaker cam sets on the bottom of the exposed upper crankshaft.  This cam is held in place by the bottom 1/3rd of the flywheel key.  This allows only the upper 2/3rds of the key to engage the flywheel.  I have seen it on (2) 1974 9.9s where the flywheel key repeatedly gets sheared off, but the rest of the key is intact inside the breaker cam.  Both of these flywheels had apparently gotten slightly loose over time & the tapered hole wallowed out slightly where it was mated to the crankshaft taper.  This left a slight ridge (approx. .006") on the upper inner edge of the flywheel hole.  Even if you tried to over tighten the flywheel nut, the flywheel could not be sucked down tight enough on the crankshaft taper to prevent future repeated key shearing.

 

My cure was to use a medium sized 1/2 round file & carefully file off this upper ring (unworn metal) inside the flywheel hole.  This now allows the flywheel to be seated ever so slightly deeper & snugger on the crankshaft.  The later motors do not rely on this breaker cam & I suspect the flywheel hubs are made slightly longer to eliminate this problem.
 

Ignition  1974 thru 1976:  These motors have transitioned thru 4 electronic ignition systems. The first 3 years from 1974 thru 1976 has a straight magneto setup with points and condensers, but does have external coils, which are energized by what's called a "Driver Coil" located under the flywheel.  All OMC models that utilize points, will have them set at .020.  This point setting is usually stamped on the armature plate under the flywheel, & on the inside of the flywheel, so if you remove the flywheel you can see this setting. 

 

For a complete worksheet on how to set & adjust the points on these magneto ignition motors CLICK HERE
 

Ignition  1977 On: Then  from 1977 thru 1984 they have electronic capacitor discharge ignition, sometimes called a CD ignition, or as OMC calls it, Mag Flash ignition.  This has a charge coil under the flywheel that sends a small voltage to the power pack, which ups the voltage to 300 volts & is then sent to individual coils & then on to the spark plugs.  From 1985 thru 1988 a slightly improved version of the system was used that was called CDII.  Then from 1989 thru 1993 another system called the UFI (Under the Flywheel Ignition) was used, this incorporated the powerpack built into the electronic ignition that used a trigger sensor and it's all located under the flywheel.   This can create another whole different trouble shooting system if parts of the system fail.
 

 

It appears Bombardier now only offers a conversion kit to convert the 1989 - 1992 units back to the previous CDI system with the powerpack being mounted on the side of the head with only the trigger sensor & charge coil mounted under the flywheel.   It seems that during those 3 years, when OMC used the UFI with the powerpack, charge coil & trigger sensor being integral & mounted as a sealed unit under the flywheel that the weak link was the trigger sensor.  I suspect this could be a plus later down the road where replacement parts could be more readily available after the initial investment of the conversion.

 

Power Pack:  The usual problem if the motor dies & refuses to start with no spark, may be traced to a bad power pack.  And this power pack can fail with no forewarning.   I have had an aftermarket one go bad after 75 hours of trolling time.   Apparently if you use the motor basically for trolling where the motor never really gets to turn up to a higher RPM, the power pack builds up internal heat, giving it more of a chance to break down internally sooner & short things out.   Therefore, if you use your motor strictly for trolling, be prepared & possibly acquire another power pack.   Cost of a new one is between $60.00 to $72.00, or you my pick a used one up for about $20.00.  However the service manual says there is no testing of the powerpack that will tell you it is good or not, but after testing everything else & it still does not start, replace the powerpack.

 

I have a friend who stored his 9.9 in a heated building over the winter only to have the powerpack fail the next summer when he tried to start it.  The only thing I could come up with was that maybe it was on the verge of failing when he took the motor out of service & just setting in a heated room allowed the internal components to break down & short out.  ??

 

The electrical output plug will have a rubber boot with pins protruding for a male/female fit.  Depending on the year there will be 4 or 5 pins.  The center pin is the kill wire which is black with a yellow stripe.  This wire goes to the kill button.  I have ran into the situation where you may have gotten the wrong year of powerpack & had 5 pins on the powerpack side but only 4 pin receptacles on the timing plate /stator wires plug.  Here I drilled out the 4 pin unit in the center with a 3/32" drill to accept the 5th pin plug from the powerpack.   I then cut the powerpack wiring harness back just enough to solder another wire onto this black/yellow stripe wire, taped it back & ran that wire to connect to one wire of the kill button.  The other wire from the kill button is just grounded usually to the port motor mount & all the kill button does is ground out that wire.

 

The power packs will be marked CD 2, with the 2 indicating the number of cylinders it is designed for.  On a 70hp 3 cylinder, it would be CD 3.  The V4s use 2 of the CD 2s.   OMC lists the same powerpacks for the 2 cylinder motors as being used for from 6hp to 55hp motors made from 1977 to 1982.   Aftermarket power packs may not have this coding on them.

 

Coils:  The coils on this model, one for each cylinder, are bolted on the LH rear side of the motor block.  As you may suspect the top coil is for the top cylinder.  These coils have a orange & a black wire coming from them along with the spark plug wire.  The black wire is the ground.  The orange wires are the high tension wire.  The orange wires will have a dark stripe on them, with the top coil originally having a black stripe & the bottom one a blue stripe.  These wires go into a black rubber coupler that has 3 prongs in it.  The prong placement is identified by "A", "B" & "C".  The orange coil wires need to be in their respective locations in this coupler or the timing will be off.  The top coil wire needs to be in "B" socket & mates to the orange /black stripped wire in the other half of this coupler. The black wire "A" socket in this coupler is for the kill switch.  To remove both the coil assemblies, you may need to cut this black wire, (depending of it is a pre 1977) & then crimp on a "bullet type coupler" on each end for later continuity on reassembly.  The later ones have a connector.

 

Spark Plugs:  Spark plugs for these motors need to be 14mm threads with a 1/2" reach.   They REQUIRE this thread length at 1/2".    They will have a 13/16"hex body.   The plugs recommended here will fit the right "reach" length.    If you try to put anything longer in, they will reach too far inward & hit the top of the piston.  This can possibly poke a hole in the piston when the motor starts, making for a complete tear-down to repair it.   

To do a spark test, remove the plugs with a 13/16" wrench and see if you can get the spark to jump from the ignition wire to a source of ground across a gap of at least 1/2 of an inch.  When you are doing this, either leave the other wire on the spark plug or be sure to ground the ignition wires that you are not testing so that there is no damage to the CD modules.  It is even better if you can rig it so that you test both ignition wires at the same time.  Using this method, it is easier to notice if there is some erratic pattern to the spark.  There is a picture of a home-made tester on the "Trouble Shooting" article.

 

It is not unheard of to have a bad new spark plug, but rare.  These motors if in good shape will run surprisingly well on only one cylinder, but will not have any power.  It is a lot cheaper & easier if you get the motor only running on one cylinder, (or even intermittent running on one cylinder) to swap out the plugs first thing on the agenda.

 

The consensus from many users for many years is that the Champions plugs seem to work better on these motors, at least the newer motors using the electronic ignition.  Now that the Japanese plugs have made the scene, this has changed somewhat in relationship to the magneto style OMC motors of this series (1974-1976) as they seem to run better using NGK BR6HS.

 

The spark plug wires on some of these motors usually have an original plastic tape on them with the recommended spark plug number.  Depending on the year, this tape may recommend different plug numbers.  If the recommended number is Champion L78V which will be the new number of 833M, this is the non-electrode "air gap" or "surface gap" plug that fires in 360 degrees to the sides of the plug.  Champion has changed the code system from what I was used to & now they do not really tell you which is a hotter plug, but they list a L76V or the new number of  827M, I assume this may be hotter than the L78V.     These plugs have an air gap in the insulator that is suppose to increase spark, but as the motor's ignition system gets older & somewhat weaker, the system just can't put out the voltage needed to effectively fire this type of  plug.  If you go out and run Wide Open Throttle all day, and just slow down when its required by law or you come in to the dock, then you should use these air gap plugs if your system is strong enough.  If you run slow using them, they will oil foul more easily as they have no idle bar.

 

To check the recommended spark plug for your outboard, CLICK HERE.

 

 

Then other models, at least the 1983 will have the tape recommending Champion L77J4 plug which would be the  corresponding conventional single electrode Champion plug.  You now may have to use  L77JC4,  or it's newer replacement #821 or the 821M for marine use.  If you can't get the "M" series, don't worry, as it is probably  just the outer metal coating that may be more resistant to salt air.  If you are using the motor to run to the fishing area and stop to fish or troll slowly for extended periods of time, these plugs are probably the better choice as they tend to not foul as bad as the air gap plugs do.   So, use the above information as to your usage to determine the plug you need, NOT necessarily the recommended one on the motor.

You may find a recommended plug of  QL77J4, this is the same plug but with a resistor or sometimes called a radio noise suppressor plug.  It would be recommended of you are running a VHF radio or sonar/depthfinder.

 

The spark plug gap for the OMC 9.9 /15 is the same on all 74 thru 2000 recommended being set at .030.   Depending on what book you look at, the recommended plugs & gap settings may vary.  One book recommends Champion  plugs  for 74-76 , being #L81C, while the 77-98 are QL82C.   This .030 plug gap works well for high speed running, but an old trick used by trolling fishermen is to re-gap them to .040 to help keep the plugs from fouling.

 

The NGK brand also makes good spark plugs, the recommended one for these motors being #BR7HS (resistor), or the newer Iridium series #BR7HIX, gapped at .030 will also work.   However the common recommendation is to go up one hotter plug to #BR6HS.  The Iridium series has a smaller diameter electrode, which should make for a hotter & cleaner spark. 

Replace Spark Plugs or Clean Them?   What's the rule of thumb when it comes to replacing spark plugs ?  Run till there's a problem, or replace them once a year, every other year, etc. ?   There are lots of opinions on this one.  Spark plugs are cheap so some folks just replace them every year.  I personally clean & beadblast them, check the gap and put them back in.  If I do replace them every 2-3 years, (depending on how much I run the motors) I save the old plugs for spares, sandblast them so they are a usable spare set & vacuum pack them to keep corrosion off.

If you do replace with new spark plugs, be sure you get the same configuration so that you do not have a problem at the start the next boating season.  

Rectifier For Recharging if Battery of Electric Start Motors : These motors alternator produces 300 Volts AC current, to convert it to 12 Volts DC there is a rectifier installed in the line.  Leading from the power source under the stator / flywheel will be 2 sheathed cables.  One with orange wires goes to the powerpack, in that cable will also be a black kill button ground wire.  The other sheathed cable will have 3 yellow wires leading the the terminal block.   These will be 1 each of a yellow wire, 1 yellow with gray stripe & 1 yellow with blue stripe.  These need to be connected to the terminals of the terminal block to the same color wires going to the rectifier.   Coming from the rectifier is a red wire that again goes to the terminal block.  This red wire is then ran from the terminal block to the electric starter HOT side so it will charge the battery.

 

You may find a rectifier that has an other wire that is usually blue or possibly black.  This wire usually goes to the kill button on some versions of electronics.  These rectifiers are pretty universal on many sizes of OMC motors, & if the boat is equipped with tachometer the yellow/grey wire usually goes to it.

 

If you hook up the wires to the battery backwards, you will more than likely ruin the rectifier.

 

 

Installation of Hour Meter or Tachometer

Throttle Block : These motors are designed so that you can not manually start the motor (pull the rope) if the throttle is advanced much beyond the start position.  There is a dog (or interlock) lever on the top or side of the manual starter spool that drops down & engages in a ratchet that prevents the starter rope from being pulled.   These early (pre 79 motors) the ratchet notches for this neutral safety interlock are on the top of the starter spool, this interlock dog is activated by a linkage from the carburetor roller cam.

 

Therefore it is wise to, each time you are going to start these motors to twist the throttle to the slow side & then bring it back to the start position.  The reason for this is that since there is some slack in the throttle pivot gears.  Many times, just bringing the throttle twist grip back from the fast position to the start position, the linkage has not reset it to the neutral safety position. 

 

You can pull the starter rope handle right off the end or break the rope, if you jerk the rope hard enough & are not suspecting that the thing is locked in the safety position.

 

 

Neutral Safety Position:   The electric start versions also have an electronic neutral safety switch, which is an inline switch between the actual starter button & the starter itself.  It is activated by the bottom of the spring detent plate that holds the shift lever in or out of gear. Occasionally if the motor will not start with the shift lever in neutral, check this switch.  The mounting bracket for this switch bolts to the side of the block below the fuel pump of the pre- 88 motors.  Loosen the bracket & the bolt holes are sloppy enough that you can usually get the switch button aligned so the bottom protrusion of the cam plate will push the button down when the shift lever is in neutral.

 

Do Not Force Shifting Lever : One thing to be aware of on these motors, is that the clutch dogs in the gearcase's transmission are rather large in relationship to some other models.  This is good in that you most likely will not experience the motor jumping out of gear because of worn clutch dogs if the linkage adjustment is not properly set.  But also at the same time, it means that you should NOT TRY TO FORCE the shift lever into a gear while the motor is NOT RUNNING.  You could very well break the shift lever, especially the newer plastic levers, or bend some of the linkage if the older metal lever.  If you HAVE to place the transmission in gear with the motor not running & the shift lever does not want to engage, try slowly pulling on the starter rope just enough to allow the clutch dogs to mesh in the gears. 

 

Rev limiter if in Neutral & Reverse:  On the timing plate there is a metal plate behind the actual throttle cam plate.  This is a stop lug that when the shifting lever is in neutral that the motor can not run at a high speed & possible ruin the motor, or if in reverse could create a safety issue.  This is essentially a Rev limiter.  It was not provided on the earlier motors especially probably pre 1977 that I have seen.

 

 

Motor Makes More Noise Than Normal :  The 1st, & many times not as obvious, would be to be sure the insulation is still inside the motor hood cowling.  After that then look at the following things.  (2) Has someone has repaired the lower unit, like replacing the water pump, they may have left out the exhaust baffle (note that there is no baffle in the 74-76 motors).  This is discussed in a later section.  (3) Also it could be that the upper motor mount seal/grommet is deteriorated enough that it may be letting noise, (& oily residue) leak out.  This is a rubber seal that is located between the upper rear of the pivot shaft housing & the upper exhaust housing.  At this location on the exhaust housing on each side you will see a 1/4" Phillips head screw on each side.  These screws go into the upper rubber motor mount that is located inside the housing.  The grommet is the seal between the pivot shaft & the housing.  The above 2 conditions will have more of an exhaust type sound.

 

If you have a tinny type noise or rattle, then it could be  (4) The pistons may be worn & could have lots of slop in the cylinders.  This however will usually quiet down as the motor warms up & the RPM is increased.  (5) The flywheel could be loose, but this will be more of a knocking type rattle.
 

Also look & see if the foam insulation is still attached to the inside of the cowling.

 

Prop Spins While out of Gear Using Flushing Muffs:  When the engine is running in neutral using muffs & not in the water, the driveshaft will be spinning internally in the gearcase.  The driveshaft is direct from the motor & goes through the water pump and down into the gearcase where the transmission is.  The top or input gear is called the pinion gear, it engages both the forward & reverse transmission gears simultaneously.   These gears are spinning all the time the motor is running.  When the sliding shifter dog which is splined onto the propshaft is moved to engage either the forward or reverse gears is when the propshaft is then locked into the appropriate gear.  The prop spinning in neutral is a result of the movement of the gear oil in the gearbox caused by these spinning gears which is totally surrounded the gear oil even though it is not in gear & as a result the prop may slightly spin.  This is perfectly normal.

 

 

Water Not Coming Out of Overboard Water Indicator Hole:  The one thing that will be the most likely need to replace is the water pump impeller.  If your motor is 1977 or later & you get no water spraying out the "overboard water indicator " (tell tail hole or pee hole to most boaters), get a small single strand wire & poke it in from the outside of this hole while the motor is running.  There may just be slight salt water crystals, or if it has set for a while, maybe a bug crawled up there.   If your engine overheats & this overboard water indicator is not spraying, shut it off & look for debris plugging the intake screens on the sides of the lower unit.  Start it up again & again look for water spraying out.  If you can NOT get water coming out this hole, then SHUT IT DOWN QUICKLY.  If you get steam coming out this hole, you DO NOT have water being pumped.  Do not let it run to where the engine block is so hot you can not place your hand on the top of the block without getting burned or the paint starts to scorch., as you WILL ruin the rings. 

 

If there appears to be nothing plugging the water inlet holes on the lower unit, be careful as the screen behind these holes is merely plastic.  And you have checked & cleaned the tell tale hole and there still is not water showing, then in all probability the impeller is aged, worn or damaged.  One thing that will wear the impeller more than anything else is to start & run the motor without any water going thru the pump for even a few seconds.  It needs the water flowing thru it to lubricate this rubber impeller.  If run dry, the ends of the impeller can get worn/melted off, & or the nylon impeller housing can get melted & between the impeller rubber & melted nylon, plug the water pump outlet.  This chewed up rubber can then get forced up into the upper water supply tube where it enters the block possibly blocking flow, if this rubber debris makes it into the water jackets of the motor, again possibly making a blockage that is hard to remove without about a total teardown.

 

If you are running it in a barrel & get erratic water flow out this tell tale hole, you might consider pulling the motor out & checking for debris plugging the water intake screens.  You may have to dump the water & start over with a cleaner tank.

 

For more detailed information on water pumps look at our "Lower Unit" section.    CLICK HERE
 

Water Passage Route in the Motor :  As shown in this 1978 repair manual page shown in the LH photo below, the water is sucked into the lower unit thru the screened  holes in both sides of the gear case unit.  It goes up & into the water pump.  From there it is pumped up the supply tube to a block that is bolted to the underside of the power head.  From here it is directed into the bottom of the water jacket on the right hand side of the power head.  Some of the water can go out the overboard water indicator tube.   This overboard water indicator is commonly called the pee hole by many outboarders.  The water coming out of it will not be hot because it has not had time to circulate thru the block's water jackets.  It may be slightly warm but probably not enough for you to really tell if your put your hand in it.  It may be slightly warmer before the thermostat opens allowing more water to flow thru the motor.

 

The majority of the water goes up in this water jacket & then back down & into the block.   Here it circulates around the sides of the cylinders, up & into the top of the head & thru both sides of the head & into the thermostat.  Then out the thermostat, (which should open at about 145 to 160 degrees F.)  up thru the water cover plate on the rear of the head & back out thru a passage in the head & out into the exhaust housing to be either sucked out thru the prop hub or thru the holes in the sides of the lower unit if the boat is not moving.

 

 

Once the water exits the block, it flows down inside the exhaust (mid section) housing, out thru holes in the sides of the lower unit & also out the prop exhaust.  There have been changes in this flow over the years.  The early units as shown in the photo below on the left used the square exhaust pipe.  The pre 1981  15 hp also used the square pipe.  Approximately 1981 saw usage of the round tuned exhaust pipe for all the later 15 hp motors.  And later nearing 1990 this tuned pipe was used on all 9.9 & 15 hp motors.   You will note that the early square pipes did not have a separate 3/8" copper tube exhausting the flow farther down inside the actual exhaust housing, but only let it spill out at the base of the motor inside the housing.

 

As shown on the right of the photo below, the newer motors used this round, tuned exhaust pipe, & they also have added a short 3/8" copper tube diverting the exhaust water farther down inside the exhaust housing.

Not shown below is an last exhaust pipe, used starting approximately 1986 that was very close in appearance to the round long one but only about 6" in overall length.  It used the short 3/8" copper tube only, but about 1/2 the length shown on the RH one below.

 

 

No Overboard Water Indicator as we Know it, for the First 3 Years of Production:  The water simply was pumped thru the motor, then was exhausted out the bottom of the powerhead into a split section in the exhaust housing.   There is a rear chamber in the exhaust housing that is only open on the bottom, slightly below the one 3/8" blubber hole on the outer rear of the housing.   This system was common to all the earlier OMC engines prior to these years & was carried over into this series of motors thru 1976.   With this older system it is can be hard for the inexperienced to tell whether your water pump was really working until the thermostat opens allowing hot exhaust water out the blubber hole, as as compared to a motor that uses the newer tell tale system.   After the thermostat opens, you get lots of hot water & some exhaust gasses out this 3/8" blubber hole.   The one thing I have found however is that at an idle there is not much water blubbering out this hole.   If you are not certain, if the motor runs & the block does get so hot that you can not hold your hand on it for about 1/2 a minute, or the paint on the upper rear block starts to burn, the water pump is bad & needs replaced.

 

On the pre 77 motors the blubber hole exhaust chamber is open into the 6 holes on the rear sides of the lower unit, forcing the water out the blubber hole or being sucked out the lower holes when in the water.   Later motors used a exhaust baffle plate (with numerous holes in it) at the lower end of this chamber, this apparently allowed for better breathing of the newer motors since the overboard water indicator pulled water off at a different location.

 

Back pressure from the exhaust inside the total housing forces some of the outlet water up & it pushes a combination of exhaust gasses & a watery mix out this upper indicator hole.   When running right & with the boat in the water, (which places back pressure on the exhaust) there should be considerable water mixed with some exhaust blowing out this hole.   If you however run it using muffs, you will get very little spray water out this same top exhaust relief hole.    Without exhaust back pressure, all the water that is exhausted goes out the bottom & out thru the prop.

After the motor warms up, if you can lay your fingers on the flat place on the top of the block at idle RPMs and hold them there for about a minute without a great discomfort to them, (as the thermostat opens at about 150 degrees) if your engine is running about right.
  

From looking at parts & service manuals for 1974 thru 1976 it is my observation that the "New Overboard Water Indicator" was not introduced in this series until possibly late 1976 or early 1977.  I have one 74 powerhead that has no provision for any overboard water indicator of any kind, but I have another with a model number suffix of G, it has a modified water jacket that has an 1/8" pipe fitting tapped into the upper section.  It also has some sort of a formed plastic spacer that goes over this section & the tapped Ell 1/8" pipe fitting going thru both.   This main water jacket area is thin & possibly the plastic was designed to help eliminate leakage.  This threaded hole is located in the upper mid part of the water jacket.  This location could only have been used for a manual start motor as it would have been in the way of the wire connection terminal block of an electric start version.   My assumption is that this is was NOT a factory modification, but an owner or dealer modification.  Then I have another same year motor with a prefix S, that has a raised threaded boss like the later versions on the lower section of the water jacket.  The simple method of converting would be to replace the outer water jacket with a newer one with the pipe thread outlet & drill a 1/2" hole in the rear of the lower cowling with a rubber tube connecting them.  The photo below shows the normal outlet position of this modified jacket.  All the 1977 motors that I have seen do have this Overboard Water Indicator.

I would recommend anyone having one of these older motors without the "Pee Hole" to convert it to the newer style, as the is no doubt then if the water pump is working or not.   However taking a page out of the newer motors design, it may be best to consider placing the outlet Ell nearer the top of the water jacket cover.   The reason here is threefold in that (#1) it is easier to rout the hose, plus (#2) it may eliminate a vapor lock in the upper water passage, that could slow down the initial water passage into the block.   And (#3) this sideplate can not be taken off the powerhead UNLESS the powerhead is removed from the midsection because you can not get to the lower front bolt under the rubber motor mount.

 

This hole can be drilled & tapped at the upper location while this sideplate is still on the motor.  I would however place some chassis grease on the drill to pick up most of the chips when drilling.  Also do the same on the tap when tapping.   I would use a starter drill of about 3/16" & then finish the hole with a R drill (.339 dia.) or a 11/32" (.344 dia.) drill & tap to a 1/8" pipe thread.  This material is thin, (less than 1/8" thick) & there is a cavity behind it that gives enough room to drill & tap, but don't tap it deep (only enough to get a few threads in the jacket) as pipe threads are tapered & you need to have this fitting tight & pointing down & rearward when finished.   If you don't get it deep (large) enough, you can always tap it deeper.  It is rather hard to make it smaller if you find you made it to deep/large.

 

Since pipe threads are tapered, tap it in only about 1/8"to start & then try the fitting.  If you happen to go too deep it may bottom out inside & you would then have to shorten the Ell threads of the fitting.  A 1/8" pipe Ell with a 3/16" barbed hose fitting is what you need.  The OMC Ells #321886 are made of Nylon, & are recommended as they are more forgiving if you need to tighten more. Apply some non-hardening gasket sealer to the threads.  If you do need to tighten it in more, you may have to file off some of the metal or Nylon off the threaded screw boss just in front as the Ell barbed fitting may hit it while rotating & you can't get it rotated enough.

 

One problem with this upper location is that you can not use this location if the motor is a electric start version because it would interfere with the electrical junction block from the power source, unless the upper junction block screw was removed & the junction block was rotated downward slightly & then only use the rear screw to retain this junction block.  Not really a good thing.

In the photo on the left below, is an you can see the actual modified Overboard Water Indicator using a OMC Ell.  The bright aluminum protrusion at the bottom of the cowling is simply a aluminum rod with a .085 dia. hole & the barbed end lathe turned to just have a snug fit inside.  The tubing is clear vinyl  5/16" OD (just the same size as the hole is drilled into the cowling).  An O-Ring of a tight fit is slid onto the tubing to form a stop for the tube's protrusion out of the cowling.  The beauty of this is that IF the outlet hole becomes plugged, this tubing is flexible enough to be pulled upward out of the hole & easily cleaned.

 

In the photos below you will see the differences between the early non tell tale hole & later water jackets.  On the right at the red arrow you can see the threaded hole for the water outlet Ell of the newer jacket.  You will also notice the lower right bolt hole, which is the one you can not get to without the powerhead removed.

 

 

This outward hole in the 1977 & later plastic overboard water indicator is small enough (.085 dia.) which is about the size of a wooden matchstick, small enough as to not draw off a high volume of water.  From there, the water is routed up the rear of this jacket, over the top, down & into the block.  The flow then splits & goes on each side of the cylinders & out the top into the water jacket of the head.  The flow splits again & circulates around the inside of the head’s water jacket & out the bottom to the thermostat.  It then goes out the thermostat, when the proper temperature is reached, up to the top & then back down the thermostat water jacket, into the lower head & then into the lower block & out thru the exhaust housing’s divided section, out the baffle & then out thru the 4 holes on each rear side of the gear case above the cavitation plate. These holes are there so that when the motor is being run in the water without being in gear, the backpressure is vented out thru these holes.  When the motor is in gear, the prop is turning & the boat is moving forward, this backpressure is sucked out thru the center of the prop.

 

Even after the new overboard water indicator (tell tale) was implemented, the old vent mist holes were left in the upper housing.  They may have changed from one to two & in size, but they still are there.   The later ones (1992) have a plastic cover that acts as somewhat as a muffler.   They are there yet probably as simply a relief hole so internal exhaust pressure will not build up inside the upper housing. 

 

 

This indicator water when the motor is running should be not that much warmer than the water the boat is setting in, as it is just an indicator that the water pump is functioning & is exhausted from the engine before it has a chance to warm up.  So, if you DO NOT see any water coming from this overboard water indicator hole, AND you are sure the hole is NOT PLUGGED, then you most likely do not have any water circulating in the motor. With the motor running for a period of time enough to warm it up & the engine is to hot to hold your hand on for any time on the block's top, there is NO WATER  going thru the motor.  If not, or a minimal amount of water is being pumped, you may see steam coming out the overboard water indicator hole. AGAIN, NOT A GOOD THING.  The engine should be warm enough that you can place your hand on the main block for a period of time without being unbearably hot.  If it is hot, or the paint starts to burn, it is too hot, shut it down immediately & hope you have not ruined the rings or scored the pistons/cylinder walls.

 

Later in 1987 or so, the factory changed the the overboard water Ell by rotated it in 90 degrees more with the outlet pointing up.  The tube was made longer & re-routed up & around the outside of the powerpack & motor mount.  This greatly improves an access to this tube for checking if there is any question as to if the water pump is functioning.  With the tube in this position, you can, if careful, pull the tube off the outlet plastic fitting & get a better idea of where the obstruction is if there is one.  
 

Many times the blockage will be at the outlet, but the other location would be at the Ell in the water jacket on the motor.   With the motor assembled in a running situation this Ell is about impossible to get at.  With this rerouted tubing, you can apply compressed air to the tube, blowing any internal debris away from the internal blockage area.   Sure this may not be the cure all, but it can give you an indication as to where the problem lies.  Heck you may even have to blow it out a few times before whatever was blocking the hole gets broken up & flushed out.  But this is a lot easier than burning up a motor, or having to tear the powerhead off just to clean a dirtball. 

 

 

It has been observed that before the motor gets warm & the thermostat opens, the overboard water indicator hole spews more of a volume of water than after the thermostat opens.  Since the thermostat is near the last spot in the water cooling system, when the thermostat opens allowing a flow of the water to pass out of the motor.  This then lowers the pressure slightly at the overboard water indicator hole.

 

I have come up with a new tell tale unit that makes a lot of sense.   Here I use the rubber grommet off a 1992 motor that fits in the lower cowling, I then lathe turn a aluminum or brass nozzle that just fits this grommet & extends out about 3/8".   I make the upper end the size that it just is a snug fit about 1/2" into the overboard exhaust hose.  This hose & nozzle is then just lightly pushed into the grommet with the nozzle being the pee hole exit.  In use, if the hole gets plugged with debris from the motors internal water jacket, all I have to do is pull this hose up & out of the grommet as indicated in the RH picture & pull the nozzle out of the hose, freeing any debris.  No wire poking in the hole that just pushes things back into the hose.   This is just held in place by friction at the grommet &  on the nozzle from the hose.   You might have to replace the hose with a more flexible one if yours is hard.

 

Note, DO NOT use light clear plastic tubing (sure it makes sharp bends easier, but) for the conduit for connecting to the water jacket to the nozzle.  I did this once & the water was hot enough that it heated the plastic enough that it swelled up & blew a hole in the now thinner walls, spraying hot water all over the engine.  Rather bad it you are running in salt water.

 

 

Replacing the Thermostat : It is advisable if you are having water pumping problems to also take a look at the thermostat, since if the water pump impeller had gotten any of the vanes worn off, this is a location that this chewed up vane rubber material can collect & plug things up.  If your motor is older, you may consider replacing the thermostat anyway.   The word is that the newer thermostats are constructed of a better material & operate better than many of the older ones.
 

 

The thermostats are supposed to open at about 160 degrees F.  which will allow the head to heat up just above the point that you will want to hold your hand on it for much more than maybe 10 seconds.  If it gets hot enough that you can smell burning paint, shut it off as the motor is too hot.

On the motors before 1986 this thermostat is located in the lower portion of the outside rear water cover, which is bolted onto the rear of the head. The thermostat is in the very bottom of this cover. The cover can be removed from the motor without removal of the power head.  BUT you will have to remove the rear cover latch to allow enough room to access the lower RH cover bolt to be able to remove this cover.  You may have to modify a wrench by thinning it as there is minimal room.

 

This can be a little tricky in that you need to keep unscrewing the latch screw (1 flat at a time) from the inside & pull the latch lever rearward so that the screw is totally unscrewed allowing the lever to be retracted rearward out of it's hole.   Once you get it about 1/2 unscrewed you can hold onto the bolt head & unscrew the latch lever.  Now the inner actual latch can be pulled out after it falls off the screw, which then the screw is free allowing the thermostat cover to be removed.

 

The problem for reassembly is usually that the wafer washer is hard to get aligned over the lever shaft AND then get the latch aligned with the flats coinciding with the flats on the shaft all at the same time.   I have found it easier to get the bolt & flat washer angled in place & then have someone with skinny fingers place the latch & wafer washer over the bolt while the bolt is then poked rearward but not out the hole.   At the same time push the lever/shaft in the hole, trying to align everything.   Rotate the lever as much as possible trying to get at least one thread started.   Don't worry about the placement of the latch until you get the bolt pretty well tightened, but still allowing clearance to slide it onto the flats.   Once you have the threads going, you can rotate the lever & at the same time tighten the bolt head with a wrench, speeding up the process.

 

Better way submitted by John Modic.    Make up a piece of all-thread the same overall length as the original bolt including the head.   LocTite the threads into the latch lever, line up washer & latch on the inside, push the lever with the all-thread bolt in from outside and place a nut on the end of the threads, tighten the nut & you have saved a lot of frustration.
 

When reassembling, you also have to have the bottom RH bolt inserted into the thermostat cover before you slide it into place as there is not enough room to do it once the cover is in place.  You also need skinny fingers to be able to re-attach the engine cover latch to it's lever properly.  It will generally be best to get the screw mostly into the latch lever before you try to align the latch flats to the lever.

 

When the factory assembled this motor the latch was in place before the powerhead was bolted on.  If I remember right it might be easier to remove the head, attach the thermostat cover & then replace the head, BUT you need to place the lower head bolts into the head before you slide it in place or you will not be able to get then in either.

There was also a change in the head & the newer cover has scallops cut (as shown below in center) to allow better access to both spark plugs in about 1977, with the cover gasket also being changed at this time because the cover went from 7 bolts to 8 bolts holding it on.   This new head was changed for better fuel burning to help eliminate fouled plugs found on the 74-76 motors when trolling.  It had wishbone shaped wedges near the plugs in the combustion chambers.  This was supposedly for revised water circulation which was supposed to keep both cylinders more even in temperature and reduced plug fouling.

 

If you have a older 74-76 motor & are having fouled plug problems, you may consider getting a later head.  Even the post 87 head will fit a 74 motor. 

Or "TIME" the spark plugs.   Orient the ground electrode towards the intake ports when you torque the plugs, the tip of the ground electrode will then face the exhaust ports (RH side looking forward). This then allows the ground electrode to shield the tip of the plug from raw fuel mist and prevent fouling and gives great low speed trolling.  Use a felt tip Sharpie pen to mark the plug so you can see where to stop tightening it so that it is aligned as described above, and repeat for the other plug.  Sometimes, you need to swap plugs to get them to line up at the right point when tightening, it's a trial and error thing.   This is also how the new Evinrude E-Tec motor spark plugs are "Timed". 
 

 

The later motors, at about mid 1987 have a different head as mentioned & shown above.  The water jacket that the thermostat is housed in, was changed to place the thermostat on the upper rear, making it a lot easier to access the thermostat.  This thermostat is all together different, in that is is encapsulated inside a plastic unit.  And the thermostat plate gasket is simply a neoprene O-Ring.  When re-installing the thermostat on these, it might be wise to add some anti-seize to the cover threads.

 

I have comparing both the old head bolt pattern for both the 74-76 & the 77-86 with newer 87 style heads.   The newer head with the top mounted thermostat could be interchanged with the older head.   If you make the conversion to the newer head, the coils may be slightly different configuration, but they can be made to function as the mounting bolts are all the same locations.

 

Do not run the motor without the thermostat.  The motor needs to come up to temperature in order for the spark plugs to to run hot enough to burn any excess mixed gas/oil so it will not foul, short out & make the motor run bad or die.   It also needs to burn the oil that may accumulate in the piston ring grooves so they do not become seized in the grooves & create more problems.  However if the motor is used in saltwater, be sure to flush it after usage as if there is salt buildup inside the motor, it WILL be at the thermostat area & if enough is there it will restrict the motor from cooling as the thermostat will become stuck shut blocking any flow of water as evidenced by the photos a bit farther down in this article.

 

 

Possible Water Circulation Problems :  One cause could possibly be is that if the motor has been run in very muddy or debris filled water, & that some of the internal water passages could be plugged. If this is the case, the restriction or blockage will usually be in the RH water jacket sideplate, (the first water jacket the water is pumped thru). However you can not take this plate off to check & clean the passages unless you remove the powerhead because the motor mount is in the way of ONE bolt underneath it.  The other area of restriction could be in the head at the thermostat.

 

If you are absolutely sure that the water pump is good, and the passages are clear, and you are also as sure that what you are seeing is exhaust exiting from the thermostat area, the following could be the cause. 

One thing you should do if no water is coming out, is to poke a wire or weed eater cord up in the overboard indicator to dislodge any debris there.  I have seen small bugs build nests in there.  If this does not do it, then possibly there is a blockage at the plastic elbow on the other end of the tube that goes into the water jacket on the motor.  The way things are put together, you can not get to the lower front bolt to remove this cover plate without complete powerhead removal.    For a link to the Water Circulation Article describing this in detail, CLICK HERE.   Go down to #6 in this article.    Another thing to look at is either the head gasket or the sealing area surfaces between the cylinder head and the block have become faulty. This would allow the combustion, the power from the explosion in a cylinder to escape across to the water jacket area, forcing its way down against the water pressure that's attempting to travel upwards. This results in a stalemate obviously and the engine overheats.  I'd suggest that you remove the cylinder head and inspect that area.

 

The pictures below are from the 1974 motor described in Story #1.  Note -- in neither picture can you see clear thru the area on the bottom, & into the thermostat location.    This area has to be clear for the water to pass thru & cool the motor.   The water pump can be going it's job, but if the passages are blocked it is the same as if there water pump was not functioning.                                     
                                       

You may have some other problems other than the obvious of a bad water pump impeller, but the above listings are the most common.   For more information on water circulation problems CLICK HERE

 

Fuel Pump Repair/Replace :  Typically this size of fuel pumps were used on about all the 2 cylinder engines in the same year range, from the 2.5hp up to the 55hp models.  The fuel pump is normally pretty trouble free device.  These pumps are activated by vacuum created below the pistons of the motor thru a hole into the inside the motor’s side plate that leads into the crankcase.  If a problem occurs, check the 2 hold down machine screws & the neoprene gasket under the fuel pump.  There is also a filter screen on the outside of the fuel pump.  

The older pumps are basically the same as the new ones with the exception that the new bodies have 2 external tabs, that align with the diaphragm tabs & other gaskets to help make it easier to assemble the parts correctly.   The repair kits do not even list a kit before 1982.  You however can use the new kits in the older pumps if you are careful & replace the new parts just as the older parts came out.  Price on a rebuild kit is about $12.00.  There are 2 spring activated check valves, one on the suction & the other on the outlet.  There is also a small spring & plunger inside all this, making it slightly hard to keep everything in the proper locations while making the final assembly.  It is suggested that you use the 2 longer attaching screws as guides in from the back side to align things before the final assembly.  Do not be surprised that you may have to do back & reassemble it a time or two before you get it right.  One word of caution, do your repairs on a clean LARGE uncluttered table as the parts are small &  may tend to crawl off & hide.  Also read & understand the instructions that come with the kit.  For a link to the fuel pump article CLICK HERE.

 

The new fuel pumps are different, from about mid 1987 on, but the old type fuel pump appear to be still used for the rope starter versions while the new type was used on the electric starter models.  The new type was moved to the LH side of the power head.  A 5/16" NF threaded hole was tapped into the original fuel pump vacuum location with a hose fitting allowing the hose to be rerouted behind the head to where the new pump is located just in front of the electric starter.  This new fuel pump was not designed specifically for this motor, as it was also being used on almost all of the larger motors of this date & on.

 

 

Fuel Tank Problems :  These engines use a single line fuel tank hose & a fuel pump that is a suction type, which has been used on OMC since 1959, therefore the vent on the top of the tank HAS to be cracked open.  The hose couplings are the same on the tank as on the motor, so be sure you attach the hose properly, allowing the fuel to flow toward the motor.  The primer bulb has 2 check valve balls inside of it making the gas flow only one direction & there are usually arrows on the bulb indicating the direction of flow.  The arrow needs to point toward the motor.  If you find where the primer bulb will not pump up & stay hard prior to starting, there is probably a air leak in the fuel line or fittings on the tank.   Also, if at  times and the requirement will be to pump the bulb occasionally to keep the motor running, this is usually an indication of a fuel line leak, as it is sucking air somewhere.  It can even be a split suction line inside the tank.   Assuming that there's no air leaks or restrictions between the primer bulb and the fuel supply, then the problem could be caused by faulty valves in the primer bulb. To check this out, with the engine running, hold the bulb in a vertical position, with the upper hose being the one that leads to the engine. This vertical position is best in order to have the internal valves work properly.  If that doesn't bring an improvement, it is strongly suggested purchasing a new primer bulb assy. 

 

Another situation is when the boat & motor is setting for a while, & if you leave your fuel line attached to both the motor & the portable tanks full, WITH THE TANK VENT CLOSED, that when the weather gets warm, the pressure inside the tank will force gas up into & past the carburetor float & in to the engine.  This excess gas will then leak out & down the exhaust housing, mixing with carbon inside this housing & cause a black oily residue to ooze out of the motor.

 

There can at times be other problems related to heat & gas vaporizing in warm weather.  There is the possibility it could actually pop the internal ball valves out of one end or the other of the fuel connectors, plus possible internal damage to the fuel line bulb.  Some boaters when leaving the motor set for a while, will push the ball in with a pencil to relieve the internal pressure on the fuel line.  It is best to get into the habit of unplugging the fuel lines from both the tank & the motor when not being used.

 

When the engine is running, the fuel primer bulb should NOT be firm, as when you primed it.  When the engine is running, the bulb is usually laying in somewhat of a horizontal position & the fuel simply flows through it (more or less about half full).  If you find that the bulb is hard, the fuel valve inside the bulb probably has come apart & the inner portion fallen out, turned itself around, & or then pulled back inside the valve housing.  In effect this is shutting off the fuel supply.  Also many times the primer bulb can, over time, get hard enough that it is hard to prime the engine  If this is so, it is probably about time to replace the whole fuel line assembly as the lines usually then also be getting hard.

 

Some of the older Tempo plastic gas tanks with unitized fuel gage and fuel pickup with the rectangular clear plastic viewing dome, may WARP after a period of time and the neoprene gasket underneath does not seal anymore. If the tank is exposed to the elements, when it rains, the water runs in on the top of the tank around this seal where it collects.  This can be checked by simply tipping a full tank & if gasoline leaks out around the gauge/outlet, water can surely leak in.  As a layman's fix, you can usually remove the O-ring & use silicone sealer between the tank & this bolt on flange.

 

In may metropolitan areas, disposal of contaminated gasoline cost upwards to $3.50  a gallon.  I think I could figure out a method of filtering, or straining it & reusing it in a lawnmower or something.

 

If the gas tank has been setting for some time with fuel in it & the fuel has somewhat evaporated or turned to a brown jellied mass, one method I have used to clean the internal parts of the tank, is to put some paint stripper along with some pea gravel or small rocks inside the tank.  Let it set for a day or two, then shake, twist & turn the tank repeatedly.  The rocks will help break things loose & the paint thinner helps loosen the old gas.  You might have to do this numerous times changing the paint stripper, depending on the severity of the contamination.  When it is fairly clean, dump the contents & replace the pain stripper with rubbing alcohol.  Repeat until the tank in clean. The rubbing alcohol is cheap and will also mix with any water that may have remained in the tank, so the water is removed at the same time. The alcohol also evaporates, so you do not have a disposal problem, which you would if you used gas to clean the tank. 
 

Fuel Octane Rating :   As for fuel, briefly the gas should be non-leaded, with a minimum of 87 octane rating and probably NOT ARCO brand, which usually is called gasohol.  This 10% alcohol additive may soften some of the older fuel lines, fuel pump diaphragm, carburetor gaskets & not be compatible with some current outboard motor needs.   The alcohol in the fuel will within a couple of months separate from the gasoline & will by it's nature attract water.  This is not good in a carburetor especially if it sets for a while.

The reason for mixing oil into the gasoline is that since these engines are 2 cycle, (sometimes called 2 stroke) there needs to be oil mixed into the gas to lubricate the internal parts (piston, crankshaft & bearings) of the engine, as there is no crankcase oil reservoir or oil pump as in the 4 stoke engines.

 

Less oil than recommended in the fuel makes the engine run leaner and warmer (less power, causes detonation, & overheating, but more important, could cause the motor to get so hot that it could seize the piston inside the cylinder walls), more oil makes the engine run rich and fowls plugs (less power too), forms carbon deposits & friction can increase caused by the carbon builds up, so more heat is also made.  Therefore a happy medium needs to be achieved.

 

You will see considerable discussion from time to time of this fuel ratio mix on at least one of the major boating forums.  There are some that seem to be emphatic about sticking with antiquated factory recommendations even though the oil quality has dramatically increased during the last 30 years.  It seems that if you take a page from the new automobile manufacturers concerning recommended oil changes & apply it to outboard motors there should be a parallel where the old days it was recommended to change oil every 2500 or 3000 miles, now that has moved up to 5000 or 6000 miles.  This change pretty well has to do with better engine construction & the use of newer & better oils. 

 

Black or Gray Oil Coming Out of Upper Exhaust Vent &/or Lower Unit Holes : Many of these motors are basically used as a secondary motor, & usually then as a trolling motor, and are ran for considerable length of time at a lower RPM.  The fuel oil mixture ratio of 50-1 is probably too rich for this type of usage. The black oil that seeps out of the motor is just unburned oil from the gas mixture.  The black color is coming from the carbon created during the pistons firing situation & is accumulated unburned inside the exhaust housing.  When the motor sets for a while the excess unburned oil in the fuel is mixing with & softening up the carbon, creating the black oozing oil.  You can reduce the amount somewhat by properly adjusting the carburetor idle jet to it's leanest position & where the motor runs best at an idle. 

This could be also because of a stuck open thermostat which would not allow the motor to warm up.  However thermostats that get stuck usually do it in the closed position, so a bad thermostat is usually not the cause of this condition.
 

Or, it could be a 6 gallon tank that the fuel line is still attached to the motor during storage & the outside ambient temperature is high enough to expand the fuel inside the tank to where the gas is forced into the carburetor & IF the needle valve is leaking, it will force fuel into the engine & out the exhaust  which mixes with the exhaust carbon & leaches out as BLACK oil out the prop's exhaust.  

If you are getting a thick creamy gray oil oozing out the prop hub, it is essentially the same as above except the inside of the housing may have less carbon build up & therefore the color will be lighter.   It is the same thing as described above, but possibly from a motor that may not have been run much for some time & there is not a lot of carbon inside the exhaust housing.   If there is minimal carbon built up from previous runnings, the oil will be the thick creamy light gray color that has a lot of water mixed in it.   This could also be caused by the converging ring (#332395) is missing on the prop.  This plastic ring facilitates a suction from the outside of the prop when the motor is running at a slow speed to help suck more of the exhaust gasses away from the "thru the prop exhaust" when idling in neutral or running slow.

 

 

This oil seepage may not be evident until a day or week after usage, & then will seep out up to a couple of months later.  It seems best for most boaters to then simply live with the idea that you may have to wipe it down after each usage. 

 

It is observed that if these motors are used on a smaller boat as the only propulsion, and act as a "get there" motor & also as a trolling motor, this black residue is considerably less to almost non-existent.

 

Also if the engine was winterized with fogging oil then you would expect to see oil coming out of the exhaust because this would soften any carbony buildup in the exhaust system.   If it smells like gas  =  unburnt 2 stroke oil.   However if it smells of rotten eggs  = Lower unit oil.

 

This many times may be confused with the lower unit oil leaking because of the color & location of the oil coming out.   Another reason as to this also happening is as explained above under the Converging Ring on the prop, is if this ring is missing it can hurt by not creating enough suction to pull the oily residue out of the exhaust housing at low speeds.

 

Akin to the above situation, where spark plugs have continually become fouled, I have been experimenting with using 2 gas tanks for the last eight years now & for me I am happy with the idea.  One, a 3 gal. tank, mixed at 100-1 with full synthetic oil & it is used  ONLY FOR TROLLING, the other is the 12 gal. main 50-1 tank also used for my 70hp outboard jet on the same boat.  Again, I am using the 100-1 synthetic only for trolling with the 9.9.  If & when I need to run with this 9.9 motor faster, I simply switch to the larger 50-1 tank.  However the winter of 2007/2008 in an emergency flooding situation, where I was rescuing a lady & her son who were stranded in her house & the water was still coming up fast, my main 70 hp jet water intake had become plugged with floating grass or hay, making it useless.  It was getting dark & we were caught is a strong very swift current pushing me broadside to a fence, I did not have time to change the fuel tanks as I was broadside to the current & the 9.9 was then my only source of power then.  I ran this motor at full throttle during the last half of this rescue mission for probably 20 minutes before I got to dry ground & offloaded the passengers.  As of 2011, I am still using this motor with no apparent harm.  But I was using the FULL SYNTHETIC oil mix.

 

I got the above idea from the newer VRO oil injection motors.  This VRO abbreviation stands for Variable Ratio Oil injection.   The larger motors using it (not the 9.9 or 15hp however) electronically sense the different RPMs & automatically adjusted the oil injected ratio.   They put out a 50-1 ratio at high speed & a 100-1 at slow speeds.  Recently the motor manufacturers have gotten away from this VRO system & went to a direct constant ratio pump.  This apparently is because with the VRO on a large motor with multiple carburetors, if you are idling, or trolling at the lower ratio fuel mix & you decide to pick up & run, the carburetors still has the bowl full of that low ratio mix & the engine will then be UNDER lubricated until fresh richer fuel is drawn into the carburetor.

I have kept track of the run time at trolling with this 100-1 ratio with one particular motor over a four year period & can account for 43+ hours of only trolling & with only one a sputter, all it took to clear that up was to speed the motor up until the spark plug became un-fouled.  Then 4 hours later, back home I changed the plugs before the next run.   In 2009, I switched over to using a 75-1 ratio of a semi-synthetic oil mix with the idea of not having to worry about changing tanks, but I get the black oily residue as seen in the photo above, so possibly back to the 100-1 full synthetic ratio.

 

You will see responses on some of the major outboard motor forums being very adamant to not deviate from the factory 50-1 ratio.  I realize that many of these knowledgeable persons, (many who may be old line mechanics) who may have seen blown engines in the past which may have been attributed to poor oiling.  However oils have changed dramatically even in the past 10 years.  Others on these forums expressing their concern may be just repeating what someone else has said.  And you have to consider that anyone who posts on a public forum does not want to stick their neck out, make a recommendation only to be chastised if the results turn out negative for whatever reason.  That is the way of life these days where liability's head pokes itself out.  That said, I have done the tests ON MY MOTORS for a number of years & you have read the results above.  I am happy with what I now use, but if your situation is different, then make your own decision.

 

I many times use the boat in bays which are somewhat salt water, initially I used to switch tanks to the 50-1, when I use the muffs to flush out the trolling motor at the end of the day.  The thought here is to use the richer gas to leave a better oily film inside the motor when it is stored until next time.  I now think that the full synthetic oil is so much better, that I don't bother changing, however when flushing, under these conditions, I do NOT KILL the motor with the kill button, but choke it to kill it.  This will tend to also increase the fuel/oil inside the motor if I do let it set for a while because where I live, as I normally do not fog my engines for winter storage.

 

Experiences of a Owner & Verification :  "Hi,   There is a lot of good information here. A couple of things that might be of interest to you.

I had a 15hp Evinrude that was purchased new around Nov 85 and was designated as a 86 model.  It had the plastic top carby which cracked along where low speed adjustment goes within about two years.   The motor performed well at full throttle but you had to use the choke at low speed otherwise it would stall.   I fixed it with epoxy glue and used a sealer when I reassembled it as the back corner as did warp.   It was interesting to read your article about the extra screw modification.

This model had AC lighting, cable throttle however the thermostat was located at the bottom of the head. The stop button was at the end of the handle, but did not have the kill switch.

This was a 100:1 engine and was almost always run at this ratio. The engine was used on the back of a 11ft boat and was run at full throttle most of the time. The oil was a mineral generic brand.   I put around 300 hours on this engine before it was sold and the engine was still running strong.

The main issue I had with the engine was cracked swivel brackets.  They would crack about 1cm behind where it contacts the trim pin. The first one was covered under warrantee, but I had to replace the others myself as they said it was a result of abuse.   They were $95 Australian each at the time and I fitted them myself.

I also had a issue with one of clamps stripping, which was probably due to overtightening and the fact the engine was removed from the boat after use.

The biggest disappointment with this engine was it top speed. A number of my friends had the same boat with Japanese 15hp engines.  All of them were a lot faster with one or two people aboard, however when you put 3 or more people in the boat the Evinrude would be faster.  I spent a lot of time experimenting with engine heights, trim angles fuel mixtures and even had a custom propeller made as the biggest one sold at the time was a 9x10.   In the end I gave up and bought a 25hp Evinrude which had no problem outrunning the Japanese 30hp engines of the time.

The link below will show you what type of boat it was used on if you are interested.   http://www.supaskua.com/

Cheers, Craig of Australia"

 

Checking & or Changing Lower Unit Oil :  Here are two flat headed screwdriver slotted stainless plug screws, one in the front bottom of the right hand side of the lower unit (gear case) & the other above it by 6 to 7”.  The lowest is the fill plug & the top one is an indicator of when the unit is full. 

There is another round headed #2 Phillips headed screw above & forward the lowest flat headed slotted lower drain plug screw,  DO NOT TAKE THIS PHILLIPS SCREW OUT.   This Phillips screw is the pivot for the shifting mechanism in the lower gearcase.  If you take this screw out, then the whole lower unit MAY have to be disassembled to locate & reassemble the parts internally using a special assembly tool.  However first I would try draining all the gearcase oil, lay the motor on it's side, use a stiff wire or ice pick, flashlight, prayer, beer & are VERY LUCKY while having a steady handed friend slowly moving the shifter lever to realign it so you can locate the yoke pivot hole & get the screw back in place with the inner end going into the shift yoke pivot hole.   If this does not work, then remove the lower unit so it can be shaken a bit to maybe get that shift fork pivot hole in line with the gearcase hole.

 

This shifting yoke was initially installed as the first thing during the final assembly of the gearcase.  If you can not get it aligned by the above methods, then total removal of the shafts, gears & bearings may be the final alternative.  AND YOU WILL HAVE LEARNED SOMETHING, & NEVER REMOVE THE WRONG SCREW AGAIN.

 

In the photo below this lower unit has been repainted so both of the screw heads are painted, otherwise they are normally the silver color of stainless steel.  This pivot screw is indicated by the red arrow.  The fill plug screw by a blue arrow.
 

 

The simplest way to add or change this oil is to purchase from an OMC / Bomardier dealer, a quart of gear oil in a plastic pump bottle.  The pump spout has a clear plastic tube with a threaded end, that screws into the hole that you will remove the lower screw from.

 

Remove this lower screw & check the color of the oil that comes out.  If the oil is, a golden brown it usually is OK, if it is blackish then it is probably OK, but really needs to be changed.  If it shows no water contamination, then quickly screw the pump tube into the same hole.  You will not be able to stop some oil from draining out while doing this, but if you act quickly, you will not loose a lot.  Then remove the top screw so  it acts as a vent.  Now screw the proper threaded hose fitting into the bottom hole & pump or squeeze the oil in until it starts to run out the top.  Replace the top plug.  In replacing this plug first, you are now creating just enough of a vacuum on the oil that will allow you to unscrew the oil hose & install this lower plug before a lot of oil runs out.

The manual says it takes 9 oz to refill an empty unit.  If you are just topping it off, you may not be able to add much before it runs out the top hole.  If  you have drained the oil & are replacing it, & you think you did not get this amount in before oil flowed out the top hole, you may be right.  What has probably happened is a air bubble formed in the upper cavity & pushed some oil out above it.  Usually you can let it set for a while & the air bubble will dissipate, allowing you to add more.  If this does not help, then run the motor a bit in a barrel on on muffs & try again.

While you have the screws out you should inspect the nylon seals, as IF they do not make a secure seal, water can get into the gear case here also & the price for these seals are about $.50 each.

If it is a creamy to light chocolate color that means there is water in the lower unit's gear case.  If this is the situation, then allow all of the oil to drain out.  Flush it out with Mineral Spirits.  It is suggested that you simply change oil, replace the seal washers under the screw heads & run it, but check it every so often to see how bad the leak is.  If it slight & you are not using it in saltwater, you can get by for some time or until the next winter (slow season)  by just removing the lower plug screw, allowing any water that may have collected in the section to drain out & then adding new oil.  

 

If it continues to leak, be prepared to at least replace the prop shaft seals & the drive shaft seals under the water pump.  There is also a O-Ring seal around the shifting lever rod into the gear case itself.  You should catch the drained oil & inspect it to see if there are any metal filings of any kind in it, which could mean damaged gears or bearings.  These seals are a double, back to back seals & you can not replace the outer ones only, since removal requires a internal type slide hammer which will ruin the inner seal.  Therefore to replace the seals, the whole gearcase will need to be removed & disassembled.

 

There is an option when replacing this gear oil.  You can replace the oil with regular gear oil, called Hi Vis by OMC, or now you can get synthetic gear oil.  The synthetic oil does provide a slipperier, more efficient oil that allows the gear case to run at a lower temperature.  This is usually not a big issue with these motors, as they are usually being only used as trolling motors & or as an emergency “get home motor”.  The word is do not mix regular gear oil with the synthetic oil.  If you intend to use synthetic oil, drain the gear case & refill it with the new oil.  Then make a note somewhere that you have installed synthetic oil in the gear case.

The Propeller :  OMC factory props are normally 3 blades & available in different dia. & pitches.  They fit all of the 9.9 & 15hp 2 cycle motors from 1974 & newer,  AND the 8,  9.9 & 15hp 4 stroke 1995 & newer.  They all have the 13 spline shaft size & are designed for the thru the hub exhaust.   The most often seen being a 9 1/2" X 10" for both the 9.9 & the 15 hp.  This means it is 9 1/2" in diameter & rotates one revolution in 10".    A  9 1/4" X 8" is shown for the Sailmaster & a power prop is listed at a 10" X 5".  

 

The 1991 OMC parts manual lists the following aluminum 3 blade props  --   9" X 10",  9"X 11",   9 1/4" X 8",  9 1/2" X 10",  10" X 5",  10" X 7", & a stainless in 9 3/8" x 9"

 

However aftermarket prop companies such as Michigan Propeller make other sizes also.  This lower unit can handle a prop up to 10" dia.   A 10" X 7" or a 10" X 5" seems to be a good compromise for a heavier boat, OR if the motor is used mainly for trolling, as it will not lug the motor down as much & let you go a little slower.   These slower pitched props work best on a heavy sailboat as they give more control & give a better bite for reverse.  

 

If the aluminum prop blades get dinged by hitting underwater objects, & they are not damaged too bad, you try to remove the dents out by laying the blade against some heavy metal object & lightly hammering the bends out.  Then you should file the blades edges down enough to remove any roughness or deep gouges.   New replacement aluminum props run about $50 each.

 

If you loose power but the motor continuers to run, the rubber hub inside the prop that connects the prop to the drive splines may have become3 un-bonded & is slipping.  You might be able to turn the prop by hand and see if it slips, or you can remove it from the motor and with a permanent marker draw a line straight across through the center.  Put it back on and the next time you have the lack of power problem, remove the prop and see if the lines still match or not.  If they don't it is a sure sign that the hub has spun.  These can be replaced at a cost of about $50.
 

Removing the Prop :  The prop shaft splines should be greased with marine wheel bearing  grease when reinstalling the prop, to ensure that the prop can be easily removed next time.  These props have a rubber mounted hub, so if the splines are seized tightly enough, when removing a prop, the hub can be pulled off or pulled partly off leaving the prop blades misaligned & out of balance.  The nut, a 13/16" (same size wrench as the spark plugs) needs to be snugged down so that one of the slots align with the cotter pin hole in the shaft, but not so tight that it has to have an impact wrench to remove it next time.  However a air impact wrench may be the only way to remove a stuck prop since it has a rubber mounted hub & any other method may ruin the rubber.  Be sure that you replace the cotter pin when you replace the prop.  The factory recommendation is to not reuse the old cotter pin, since it could be cracked & if reused may break & come off possibly allowing the nut to work loose & thereby loosing the prop.

 

Converging Ring on Prop :  On the original OMC & some aftermarket props, the rear outer of the prop’s exhaust hub is a plastic ring with a scooped portion pointing forward.  This serves a couple of purposes.  One is that since this motor uses an exhaust thru the prop, it then uses this ring as a scoop to force water into this center exhaust hole, forcing the exhaust away & not allowing it to build up a backpressure inside the motor at a lower speed.   This action of pulling the exhaust away will also tend to suck any of the unburned oil that accumulates inside the exhaust housing, especially if you use it mostly for trolling & do not run the motor at a higher speed for long enough time to suck the unburned oil out.   Without this function, oily residue can show up draining out the prop for weeks after it is taken out of the water. 

 

The other thing it does is that when the motor is in reverse, it again helps relieve the possible exhaust pressure

 

Over time, these plastic rings can get brittle & break off.  New ones are not expensive, about $10, & are replaced by simply laying the prop on a floor or workbench & with a short section of 2x4, & a large hammer pound the ring onto the rear of the prop hub.  The prop has a slight groove that the ring snaps into to hold it in place.  You might consider doing this in a warm room so the ring has warmed up enough to not break it during you installation process.

 

Remote Controls :  These motors were designed to be also used with remote controls.  There appears to have been 2 different OMC  "Remote Control Adapter Kits.   (1)   #386660 & (2)  # 398032.  These kits are only the adapters to the motor & did not include the cables or control lever box.  The throttle cable is ran thru the hole that normally is occupied by the kill button, & is attached to a peg located on the timing plate linkage rod.  On #398032, the kill button is moved over into the position under the RH front lower upper cowling where the starter button would have been.  The starter button is not be used in this case as if it was electric start, the starter switch would have been on the shift/throttle control box.   The #386660 kit is pictured below with it's illustrated installation sheet.  Here the kill button is moved to a new aluminum bracket that is bolted into the 2 existing holes on the front.
 
The throttle cable was ran under the manual starter spool & attached to the peg on the vertical control shaft to the timing plate. The twist grip handle was designed to be lifted into the up position, which  disengaged the cog teeth of the drive gears, allowing the cable to function without removing the twist grip unit.  This however creates problems when the motor is not operated with cables if the operator is unaware of the situation, as described later in this article. The angle that the tiller handle is mounted on the upper housing allows the handle to tip out & away from the motor for clearance.  If you snap the rubber cover off, & raise the handle, you can see that the higher the handle is raised the farther disengaged the gears become as the throttle handle's twist shaft is not on the same plane as the intermediate shaft that the mating gear is on.

The shifting cable was attached to the 2 plugged holes on the RH front side of the lower motor cowling.  And the cable end was attached to the upper hole in the shifter handle by a spring loaded twist pin.   The control cables must be type (OS) that means the plastic ends are molded on, not bolted.

 

 

Also in the LH photo below you will see a quick disconnect clamp screw that attaches the older type pulley/cable stearing system used before the more modern push/pull cable type became popular.  Shown below on the RH are the shifter split collar that goes in the location of the kill button with the cable inside it. 

 

Also in the LH photo below you will see a quick disconnect clamp screw that attaches the older type pulley/cable stearing system used before the more modern push/pull cable type became popular.
 

 

Factory outfitted remote motors could have had a electric choke solenoid if they were in the mid 1980's or later.

 

For the sail-boaters using these motors as auxiliary power where you may have to raise the tiller handle (which as noted before disengages the twist grip throttle) there may be a couple of alternatives.   The Sailmaster version of these motors designed for sail boaters is simply a extra long (25") shaft.  You could purchase a remote shift/throttle control  & mount it near the helm.  Also extending the kill button wiring to the helm area would be beneficial.  You would not really need the steerage as you already have a rudder.  You may not need the full blown remote kit as your need for shifting gears is not great, yet at times essential.  
 

Adjusting the Motor Pivot Tension :  If the motor does not stay where it is put when trolling, but vibrates & keeps moving from one side or the other, you may need to adjust the pivot shaft screw.  This is a screw that is mounted on the left hand side of the exhaust housing.  This screw has a coil spring under it’s head that you can not see.  By screwing this screw in, it tightens the tension on the motors pivot shaft.  Since it is located outside the midsection & if the motor is used in saltwater, this screw may become seized in the housing.  If this happens, avoid breaking it off in the housing at all costs.   I would, try to unscrew it, BUT BE CAREFUL that just the extended screw is what is turning.   A section in the trouble shooting repairs covers removing a seized bolt.   CLICK HERE

 

Motor Mounting Clampscrew :   The 2 clampscrews that hold the motor to the transom WILL need service occasionally.  The pivoting handles of these screws should have oil placed on the pivot pins from time to time to keep them from seizing up & then breaking off.   To service these screws, it is best to remove them from the bracket.  There is a smaller screw that comes in from the rear & is screwed into the rear of the main clampscrew, holding on the large cupped washer in place.  Use a 7/16" socket wrench to remove this smaller screw & then you can unscrew the clampscrew & totally remove it from the front of the bracket, clean, grease & replace.

 

If the screw comes out hard enough to gall the threads in the bracket, you may need to run a 5/8 NC (National Course) tap in to clean up the threads. 

 

Somewhere in production before 1983 the clampscrew handles were changed from aluminum to nylon.  The screw itself on the early models was made of aluminum.   You may want to keep these screws well oiled as replacement screw assemblies (the later screw is now stainless steel) cost $31.84 each, as of mid 2005.  In this area also later, about 1987 there were Zerk grease fittings installed in the front of the tilt hinge shaft boss, as shown in the photo above.

 

Shown in the photo below are the motor clampscrew handles.  These are the later 1987 & newer.  The earlier ones were made of a aluminum, & I have seen 2 variations of them.  The overall length of all these handles were designed so that the ends have holes in them so that when the handles are rotated with both ends pointing inward a padlock can be inserted thru both handle ends.

 

 

Not Enough Tension on Tiller Handle :  For the early motors up to about 1986, if the tiller handle will not stay where you put it, you will need to tighten it.  However this is not done as you would at first suspect.  The 3/8” nut showing at the hinge, when the handle is raised, is only a lock nut.   It has to be loosened, & the bolt's head end, that it is accessible from under the steering bracket needs to be tightened, then this visible lock nut retightened.  It is however recommended that you remove the bolt, clean the nylon bushing & apply a slight amount of grease before you reassemble it.  If you do take this bolt out, be careful that you re-engage the throttle shaft dog teeth properly when you reinstall it.

 

Cable Type Throttle Linkage :  Motors after about 1986 eliminated the gear disengage problem by going to a cable throttle linkage system instead.  The photo below shows a 1992 with the kill button on the side near the twist grip.  The earlier kill buttons were on the end of the twist knob, but the cable system was the same.

 

If this twist handle seems to not want to move, the cable may be dry & binding inside, or the timing plate may also be dry & dragging.  To test this, remove the ball socket end of the cable at the timing plate & see if the handle will now twist.  If not then the problem is in the cable.  You may be able to remove the cable & get some penetrating oil in to lubricate it.
 

To disassemble this unit, you will notice a small round hole (about 3/16" dia. ) at the arrow.  There is another 180 degrees & on the bottom.  You need to use a couple of punches & depress both of these at the same time, while pulling the handle off front-wise.  A helper can be useful in this instance.  Inside this plastic is a dual rotating cam slot which a cross-pin enters into spacers & rollers which is in turn attached into the cable end.  When disassembling these be careful to not loose these . 

 

When twisting the handle, the cable moves in or out.  This outer cable is then secured by a ball in the lower cowling.  The inner cable has a screw on adjustable end attached to a small ball socket on the timing plate.  You can make some adjustment in this linkage by moving the threaded ball on the outer cable & or at the call end.

 

 

There is a black plastic twist knob on the end of the twist handle.  This is a slow speed idle stop, (NOT A CARBURETOR IDLE ADJUSTMENT).

This can be tricky to get set UNLESS the cable is adjusted properly on the low end of the speed setting.
 

 

One thing you may look for in the cable system, is that on the end of the cable where the nylon socket is that attaches to the ball, is this cable end seems to rotate slightly depending on the position of the handle's height.  The nylon socket is threaded onto the end of the cable's shaft.  You may have to thread it on farther or less to position it so the socket is about level with the handle elevated slightly, otherwise if it twists far enough it may pop off the ball.

 

If this cable is not adjusted right you might have hard starting when putting the twist grip at "START".  Incorporated in the end of these twist grip handles is a slow speed trolling type knob that can be rotated to supposedly a slow speed stop.  I have found that this slow speed knob many times does not work, unless you do adjust the cable end also.  To set the cable end, I would put the shifter in forward & move the twist grip to where it will not go faster.  With the cowling off, you can see the neutral safety block of the shifter unit blocking the timing plate from further rotation.  I would use this stopped setting as a point to readjust the cable end so that the "START" position on the twist grip would now align with the pointer.  The rear end of the cable just snaps over a ball on the timing plate linkage.  Snap it down & off, twist it on the shaft & try.   You may have to do it a few times to see just where things line up.   Make an adjustment & the twist the grip to see what changes.

You can now adjust the slow speed knob, (on the end of the twist grip) as your slow speed stop, after you have played with the idle knob, but in conjunction this slow speed knob. If you adjust one, you may have to readjust the other if at the SLOW end of the running.
 

Occasionally you may encounter one of these cable systems that the twist grip will not stay where you put it.  The motor will usually slowly slow the speed down by itself if you let go of the twist grip throttle.  A solution for this was passed on by a retired marine mechanic.  His solution was to take a electricians #6 copper grounding split bolt clamp & simply clamp it around the throttle cable in an out of the way place.  There is enough room on the underside the the tiller handle.  Tighten the nut enough to just squeeze the cable inside the plastic sheath.   Then tape up where you split the loom with black electricians tape.  Works like a charm.

 

At this time OMC added the lanyard type kill button on the end of the twist throttle handle.  This created a problem if you used the extended universal joint tiller handle, as you could not reach the kill button with this extended handle installed.   A year or 2 later the handle was changed slightly & the kill button was moved to about mid handle left side.    This button is also a man overboard kill switch.  The motor comes with a red coiled plastic cord that is attached to a split plastic section that is inserted UNDER this button.  The other end of the cord is to be attached to the operators wrist, so that in the event he falls overboard, this insert is pulled out & the red button goes deeper in the housing & the connection is disconnected, just like turning a switch off.   In use this red button HAS to have either the lanyard insert under the button, (turning the ignition ON) or a another smaller that one called a restart clip that is inserted there if the owner decides he does not want the lanyard.

 

Zinc Anodes :  On motors from about 1983 on you may see (2) 1/4" holes drilled on one side of the cavitation plate.  These are for attachment of a zinc anode.  These anodes are threaded & bolts come up from the bottom with the anode on top of the cavitation plate. These holes are evident in the picture below of the prop shaft being removed.

Removing twisted off bolts :  Here you MAY have some choices, depending on where it is broken, & if there is part of it protruding enough to get Vise-Grips onto etc.  The other option is to just leave it broken off & go with one less bolt IF that is all that is broken, if more than one then you will have to decide if it will create a functional problem.  Many times the stainless bolts are stuck worse than regular steel bolts, because of the oxidation between the two different metals.  And stainless is a lot harder to drill than mild steel bolts.  It will be a white powder.  I have not had any luck using an easy out in any of these instances.

 

(1) If when you try to unscrew the bolt, it has resistance to where you feel it may twist off, (remember these will usually be 1/4" bolts) play it careful.  Usually if you try to use penetrating oil in this case the oil will not get UNDER the bolt head.  The corrosion will normally be between the bolt shaft & the metal surrounding it & not in the threaded area that it is threaded into.  My solution here is to use a small  angle head grinder & remove the bolt heads.  Now you should be able to pry the cover plate off these now bolt studs.

 

Now use method #2 to remove what is still in the base material.

 

(2) If you have broken it off, & it is protruding enough to get ahold of it, (1/4"), I would first soak the area with penetrating oil, If you do not have any, the best alternative is hydraulic brake fluid.  Build a dam around the broken bolt if possible with modeling clay.  Let it set for a few days & during this time, tap the protruding end with a hammer a few times.  This vibration tends to break the bond & allow the oil to soak further in.  Now try a Vise-Grip pliers to see if it will turn.  If it does, only move it slightly, & then back up, then try to loosen it again.  If you do it all at once, you can break it off again, & this time flush with the housing.  OK, this is the easy one if you got it out.  If not, then you might try to heat the aluminum up slightly with a torch in the area of the broken bolt.  Don't get it overly hot as you may melt the aluminum.  What this may do is about the same as tapping it with the hammer in that the aluminum will expand faster than the steel bolt & may help break any bond between the two.  Do the soak & tap again.

 

(3) If the above failed or the broken bolt is flush with the housing, I would again use the soak & tap/heat method, but now you have to drill it out as close to the exact center of the broken bolt as possible.  If it is a 1/4" bolt the hole size on the inside of the threads is about 3/16".  I would use a center punch & try to locate as near as possible  the center of the bolt.  Remember that this small bolt the threads being a spiral, that you will see the outside of the threads, while on the other side you will be seeing the female part of the casting as looking straight down on it.  Try to locate the center where there are no threads.  Tap the center punch lightly.  Look to ascertain if it is near where you want it.  If not then place the center punch back in the original hole & angle the head end away from where you want the hole to really be.  Tap it again at this angle & you may shift the original hole slightly.  When satisfied that is is as close as you can get it then clamp it in a large drill press or milling machine, so you can clamp the part rigidly so you can control the drilling.  If you do not clamp it securely to the drilling unit, the part WILL shift & you will drill off to the side.  DO NOT DRILL IT BY A HAND DRILL WITH NO RIGID SUPPORT.  Use a GOOD drill bit with the hopes it will drill straight & not run out to the side.  You can drill it with a hand power drill motor, BUT the odds are that you will not be able to hold it straight & the bit will wonder.  Use a cutting oil on the drill as you are drilling.  If you succeed in having it centered, the bit will go hard, until it breaks out thru the end of the bolt.  You may be able to feel the difference it at this point, as it will break into a hollow space below the broken bolt & into a deeper threaded section of the casting, as the threads will always be slightly deeper than the bolt. 

If you did not get the drill lined up exact or it shifted so the drill took out just part (1/4) of the threads on one side, this should be no problem as there should be enough to still hold.  Now you can use an ice pick or cape chisel to get under one side of what is left of the threads & work them out, & possibly use a Dremel tool with a carbide dental burr to cut the bolt shell in enough pieces to extract them from the threaded hole.  This will free the hole enough to run a tap into it & clean up the threads.

 

(4) If the above #3 failed & the drill ran out to one side, you will have to enlarge the hole enough to install a Helicoil.  This is simply a somewhat square wire tightly wound as a spring in the exact thread pitch as the desired new threads.  You will need to purchase a Helicoil kit, which includes  the proper drill size, oversize tap & an installation tool.  Here again it may be best to use a rigid drill press or milling machine & clamp the part to ensure you get it close enough to align the new threads to the other mating surface.  Here you might use a appropriate undersize end mill to clean up the butchered hole & remove what is left of the broken bolt before you use the Helicoil drill.   Follow the instructions on the tool.

 

Converting a 9.9 to 15 HP :  This question seems to pop up quite frequently & can get controversial from those who have never been associated with the conversion & are only going from what they have heard.   As you can see from the above information in this article, it is possible.  New carburetors are expensive, (over $200), but used ones go for half that, then you can probably expect to rebuild it.  Some will tell you that you need different reed valves & reed valve stops.  I bought a 9.9 new in 1978 & still used it until I recently sold it.  It is the basis initially for writing this article, & as I was trying to convert to 15 hp & there was no information, or reliable information available.  I also bought the repair & parts manuals at the same time.  From this parts manual I can assure you that the reed valves for either engine are the same for that year.   However in 1979 a .0125" shim was introduced that was placed between the leaf valve stop plate & the leaf valve itself for the 15hp motors only.

 

I have not truly tested a before /after on the same boat, same water conditions.  But will speculate that it may not be worth the price or effort to change the exhaust housing when upgrading on the older motors, if trying to up the hp to the full blown 15hp unless you can find a used housing.  Remember that the older (pre 1981s) motors still used the same 9.9 exhaust housing on both motors.    I have compared the early 9.9 exhaust tube with the later & 15hp tube.  the mounting flange where it bolts to the powerhead is different, but it appears that the 15hp can be installed & would fit.   By just by changing the housing itself, you will not show many benefits.  Tuned exhausts are well known in racing two stroke motorcycles & are very effective at specific RPMs but need to be matched to the carburetor also.  

 

Also if your boat is to large, heavy or you & your fishing buddy & gear are overloading the boat, your conversion benefits will not show.  However if you have a lighter boat & it just needs a nudge to get it onto a plane, then possibly going to the 15hp would help.

 

The larger carburetor will gain the most in increased RPM, (about 1000 RPM more, according to OMC) which in this case also relates to more horsepower.  If you insist on squeezing that last ounce of energy, then maybe the aftermarket reed valves, polishing & deburring the intake manifold  & replacing the exhaust housing will be of some benefit.  But, if you are trying to push it this far, at wide open throttle for an extended period of time, my thoughts are that then the rest of the engine may not stand up for long, so go to a larger motor.

 

Props are listed the same for both the 9.9 & 15 hp motors, however depending on the weight of your boat, it may be advantageous to try a lesser pitch version.

 

Also, as mentioned, the inner exhaust housing was changed after about 1981 for the 15 hp.  This exhaust tube on the 15hp has a circular cross-section and gets wider at the bottom, called a TUNED EXHAUST as opposed to the narrow, rectangular shape on the 9.9.  This was probably copied somewhat off the tuned 2 stroke racing motorcycle exhausts of that era.   Part of the principle was that the burned gasses also carried noise waves from the motor, if these waves created a backpressure the actual exhaust gasses could not escape as easily.  When a motor breathes better, this equals more horsepower.

Then in about 1987 another exhaust housing was brought out,  & this one is a short rounded unit & is used for both the 9.9 & the 15 hp motors.  My reasoning for the 87 date is that the 86 parts list still shows the old housings, & the 1990 list has the newer one.  This motor underwent many changes in 1987 as to thermostat, fuel pump, twist grip throttle, etc. so I am assuming that maybe (until I get a parts list) the housing may have been changed also.

On the later motors from late 1987 on thru the 1992 versions, when they changed carburetors, the inner exhaust tube is quite a bit shorter than the early ones & this same part is identical for both the 9.9 & the 15 hp versions.  Why, I am not sure at this point in time, unless it simply saves money on parts inventory & they found they gained enough by the other minor changes.

 

A reader recently made the conversion on a 1976 9.9hp Johnson using the carburetor off a 1980 15hp Evinrude.  "The carburetor change upgrade results were fantastic.   21mph GPS top speed with 9.9hp went to 27mph with the 15hp conversion on the same boat.  The reed valve shim and the 15hp exhaust will add a bit, but are not necessary to make a marked improvement o a old 15.    Do not get confused with people saying the intakes are different, or the head is different or the ignition is different.........THEY ARE NOT.   90% is all CARB".

 

Another testimony taken from the i-Boats forum, "I had a 9.9 Johnson 2 stroke on a 16' Grumman V hull, it would start to get on plane but that's about it, it needed just a bit more power.  This was in a bare 4 bench seat hull with two 250 lb men aboard and a full 6 gallon tank.

I eventually converted it to a 15hp by changing the carburetor and exhaust tube, that did the trick but it still only did about 18 mph".

Converting over to a full electric start/charge system :  This can be done, and is covered under it's own article.  To access it CLICK HERE

Shaft Length Differences :  The standard motor comes to mount on a regular boat's 15" transom.  This is designed so that with the motor mounted on the transom, the bottom of the boat is even with the cavitation plate of the motor.  The cavitation plate is the flat fin in the lower unit housing above the prop.  The difference in the longshaft unit is that it has a 5” aluminum extension the same physical size as the exhaust housing, to fit a 20" transom.  This unit is supplied as a kit, comprising the extension, a new 5” longer driveshaft, a 5” longer shifting linkage rod, a copper water tube long enough to couple between the water pump & the old tube from the power head & 6 more bolts to assemble it to the gear case.  

 

 

The SailMaster is basically the same 9.9 motor with electric start but with a 10" shaft extension for use on sailboats.  My 1981 sales literature says the SailMaster has a heavy duty reverse gears with a higher reverse thrust.  The parts list does not substantiate this however.  I suspect they simply used a lower pitch prop.   The Yachtwin, was Evinrude's version of the Johnson Sailmaster, same motor just a different color & name on the cowling.

 

Short Shaft converted to Long Shaft :  This is a common question, & to try to condense some of these repair articles I have moved this section onto it's own "Shaft length Conversions" section.

 

Repaint :  You can purchase OMC original white paint #777171 specified for 1981-1990 at about $8.50 a can.   Tempo #0204601, (Johnson White 1981 to Present) which is an aftermarket marine paint for about $1.00 less, or Krylon brand which is available in about any hardware or automotive store, in about any color you want, it may not match exactly the original color however, but it is less than 1/2 the price.  I am torn between the Krylon brand & the original, as I like the idea of being able to touch up paint scratches if the need arises.  Krylon's Ivory Gloss #1504, is very close to the standard white that most of  many of these later motors were painted with.  I have found with the OMC paint, do not try to do thick coverage or it MAY wrinkle.  Do many thin coats. 

 

The only drawback using a non-original paint is that it may not be as resistant to gasoline & gooey black oil as the factory or replacement types.  A cure for this is then a clear overcoat of Duplicolor 500 degree clear Ceramic Engine Paint from NAPA  be used.

 

The 1974 Johnson OD green color was changed to white in 1977.

 

If you decide to repaint the cowling & the rubber motor seal is OK, you can pry it away from the fiberglas or plastic depending on the year, placing matchsticks between the rubber & the fiberglas to allow for a better paint job to go under the seal.  This original rubber seal is stapled onto the fiberglas.  If you need to replace the seal (about $40.00) after repainting, to reinstall it instead of trying to staple it, just use a latex adhesive & many old wooden spring type clothes pins until the adhesive dries.

If you plan on replacing the decals, you will probably not be able to find any factory available earlier than about 1993 or 1994.  Price is about $40 for these original replacements.  If you purchase these later model decals, you will have to cut them to fit, as the newer side decals sets lower than you might think.  This is because the motors have a upper cowling that the seam is more horizontal instead of at an angle on the pre 93's.  This changes the position of the decals if used on an older cowling.  You will have to trim some off the front bottom at an angle of these side decals to get the lettering horizontally positioned.  And you will also have to trim the bottom rear decal to be somewhat close to a decent position.  Lay them out & tape them on the cowling before you install them.   You will not get a decal for the front where the control knobs are on these newer decals as there are none used on these later models. 

 

There has recently became available on e-Bay, aftermarket vinyl decals that are generic for this series of motors at a price of about $14.00 to $38.50 a set.  These generic ones are quite good, a close coloration to the later originals, but do not match any specific year.  They have the "Sea Horse"  & appear to be die or laser cut.  They are made for both the Johnson & Evinrude  9.9  & the 15 hp.  The picture below appears to be on a repainted 1983, as it does have twist handle gears & the side idle control knob.  These aftermarket ones only have decals for the back & sides, not the choke indicator, shift positions, trolling speed indicator, etc.

 

The later motors from about 1987 had the power head, flywheel & prop painted black.

 

Commercial Motors : There is mention in the Sierra & NAPA catalogs of "Commercial" 10 & 14 hp motors.  According to the NAPA catalog, they were made from about 1988 to 1991.  However I have been told of one by a reader that said it was made in 1984, plus the photo above of an 83.  It appears these are cheaper units.  They are usually painted a different color lower sections than the "standard" motors, with everything other than the cowling painted a medium gray color.   You can tell if the gray is original if the instruction decals are in white (as seen above) instead of black lettering.

 

They essentially are the same motor as the 9.9, but have only a rope starter & with a tiller throttle handle system only.  They used the older CD ignition system instead of the UFI as used on the regular motors at that same time.  There was no provision for electric start or a charging system.  

 

Some even use the older non thru the prop exhaust lower unit very similar to the older QD series.  And the NAPA marine parts book verifies this by listing gearcase O-Rings for these as the same as the 1957-1963.   My guess is that these were a sort of a "Clean Up" run made of older parts & sold thru some major discount stores, or for export out of the states.

 

Non North American made Motors :  European Johnson/Evinrude motors did not follow the year-on-year model changes as their American counterparts.  So, if you are working on one of these, & have a Clymer or Seloc manual, read it with caution, & be prepared if a few things might be slightly different.  Australian motors can also be included in this group.  The suspicion here is that any left over motors at year end, got pushed to other countries.   Also there are usually additional letters in the model plate ID.  If it was a Canadian motor, there would have been a prefix letter "C" on the model number as in,  CJ10RCDB.    For more detailed information on worldwide production, CLICK HERE

 

You may even find some motors designed to run on Kerosene.  Apparently they were designed to be sold in underdeveloped countries where gasoline was hard to obtain, but where Kerosene was used for heating oil.  They usually have 2 headgaskets to lower the compression, used hotter spark plugs & possibly a small internal gas tank for starting, & then switched over to kerosene after it is running.  These motors if shipped from the factories as a Kerosene motor would have had a "K" as a prefix to the model number.  An interesting thing here is that Kerosene has a LONG shelf life & is less of a fire hazard, so it is well accepted as propellant for sail boats that are at sea for extended periods of time. 

AC Output : Some of these motors (approximately 77-92?) could have been fitted with different stator (electric start) assembly under the flywheel that gave a AC output voltage.   We may not see any here in the US, but about all the European motors are equipped with this AC voltage feature & is normally used for the running lights on the boat that the motor does not have 12 volt electric start.  The repair manuals say the regular output to the power pack is 300 volts AC,  & for these motors, a converter is needed to make it charge a 12 volt battery.  Without me having a owners manual, I am assuming that the light bulbs would be 240 volt, which I understand is common in Europe.

 

This appears to a be a long way around to accomplish an effect, but then maybe we don't understand their ways either.  These motors appear to have the electric start ignition under the flywheel & the junction block on the side of the motor for the wires, no rectifier converting the voltage to 12 volt, but for the rope start versions NO electric start flywheel .

 

The parts manual indicates that these stators were for motors with serial number prefixes of A, B, C, or E if used on an electric start model, while the prefix would have been H if on a rope starter version.  This manual says "Serial Number prefix" however it would seem more in line with how things were done IF it was a prefix to the model number.  There was a plug in outlet on the LH rear side of the upper lower cowling that had a rubber plug cap the covered the outlet.  

 

The above pictures were supplied by a gentleman from Germany who has an Evinrude E10BACNS motor that has AC lighting.  From this I conclude to mean  E = Evinrude  10 = HP  B = Belgium  A = AC Lighting, Rope Start   CN = 1982  S = Model revision

 

Another motor, an Australian Evinrude, model  AE15BAESR was referenced in an e-mail inquiry from gentleman there that had the same 3 wire plug coming out the side.  His conclusion is as follows:  A = Australia  E = Evinrude  15 = HP  BA = AC Lighting, Rope Start   ES = 1990  R = Model revision.  
 

Here is some info that I recently garnered off e-bay.   "OMC,  AC lighting kit #584864 kit,  fits 1993-2000 9.9 & 15 hp 2 stroke engines.  This kit provides the ability to power a boat's lighting system without a battery.   Current is AC only and cannot be connected to a battery".

 

Ongoing Improvements:   Other than the before mentioned changes, there have been ongoing improvements in this model since it's inception.  The throttle cable twist grip system incorporated in about 1986, initially still used the original kill button.  In 1987 the kill button was moved to the end of the twist grip control. There is a problem with this type, if some makes of extended tiller handles are used that the owner then can not reach the kill button when these handles are installed.  In 1991 the kill button was moved again to the middle of the steering arm near the rear of the twist grip, it utilizes the safety lanyard disconnect "Man Over Board" kill switch.  If this safety lanyard/clip is missing, or pulled out, the motor will not start.  If you are using the motor for a auxiliary motor, the safety type unit may just get in the way, so you can then purchase a override, which is a small red plastic horseshoe clip called  "clip-restart" #431808 for about $3.60 which makes a neat configuration & allows the motor to run, while still allowing the kill button to be activated.

 

The SailMaster motors used a metal 3/16" rod that came out of the front cowling above the rope starter handle, went across & back in on the other side of the handle.  It was slightly arched upward in the middle.  Apparently this was to prevent the starter rope from becoming readily frayed if the motor was over the stern & lower on the transom than on regular boats.

 

Each year had a different decal, so if you have a good memory, you could identify each year this way.  The earlier Evinrudes had a different motor cowling, in that it was slightly radiused on the front & back & had a slight hump in the middle.  The top cowling for the Johnsons appears to be change slightly in about 1987, in that the upper corners have a bevel of a little over an inch all the way around the top, & they got away from the squarish shape of before.

 

 

Recommended Spare Parts:  If I was in a location where spare parts may be harder to come by, I would consider stocking the following spare parts & in the following order.  Spare spark plugs would always be a requirement.  (1) fuel pump filter cap & gasket  (2) starter rope  (3) flywheel key  (4) small fuel hose clamps  (5) lower unit drain plug seals  (6) spare prop, nut & cotter pin  (7) water pump impeller  (8) fuel line primer bulb.  If for the older 1974 to 1976, then I would add points & condensers.

 

Replacement Parts from Bombardier:  OMC sold out to the Canadian company Bombardier Corp.  in Feb.  2001.  Replacement parts for some of the older motors has dried up somewhat as the new owners may not be as committed to supplying older parts as under the previous ownership.   Now when ordering replacement parts, the dealer will see a new listing in place of  the older N L A .  This new listing is Vintage, which actually means No Longer Available.  Bombardier also changed the discount structure for many parts.  The retail prices are still listed, but the dealers get less of a discount & they now have to pay the shipping no matter what status they have.   Their website is very non-user friendly if you are trying to find parts.  The links do back to  the preceding page, & if you do manage to get to a parts list page, there is no way to identify the hp,  just the year of the motor, so you have to guess.

 

Replacement Parts from Internet Bombardier Supplier: There is one marine dealer that is set up to do internet sales & they have a very complete website that is user friendly with the availability to call up exploded views of the different parts for even motors 30 years old.   They have illustration numbers & corresponding actual OMC part numbers & prices.  Even list if any are no longer available.   Here is the link to their website

www.crowleymarine.com.
 

Another one I have found that is fast & the price is VERY competitive is http://www.iboats.com/   They carry only aftermarket parts, like coils, rings, gaskets, powerpacks, carb & fuel pump kits etc.   They do not handle throttle linkage, clamp screws, decals or many of the individual needed parts.  They are cheaper than the NAPA or Sierra & use the same part numbers & you can specify which shipping you require.   The last electrical items I priced from a marine dealer for original parts was $160.  Sierra thru an automotive store was $120 with my friendly discount, plus freight, & iboats was $106 including freight.

 

Replacement Aftermarket Parts : The Sierra catalog is available from Car Quest stores &  NAPA the catalog is available from them of course.  Many times you can get a part a lot faster by going thru these automotive stores, in that they are probably moving a lot more parts than a marine mechanic & your order can get called in almost daily.  But be advised that they will have to add on shipping, & normally do UPS or FEDX air to keep their mechanics happy.  So, unless you specify that you do not need it ASAP, your shipping will be more expensive.

 

One thing I have also found, is that these automotive parts dealers are just that, & they usually are not knowledgeable at all in the outboard applications that you may require.  If you ordered off their catalog & ordered wrong, it is your responsibility to pay for it even if it is the wrong item.  I went this route once, ordered a thermostat kit #18-3674, thinking that I also needed other parts than just the thermostat that I might not have been aware of.  What I got was the thermostat & every gasket, spring, seal etc. that would allow me to fit it to MANY different models, for a price of $25.26.  I found out later that the thermostat alone #18-3672 (all that I really needed) would have been $11.86. 

  

Also some of the NAPA gasket sets are not complete or they are misleading as to years covered.  They list the gasket set as fitting 1974-1992, WRONG.  For motors prior to 1977 if you order a gasket set, the water cover gasket, (the one the thermostat is under) gasket, is not supplied if you order the set, as there are 2 different water cover gaskets as described previously.  The older one from 1974 to about 1977, OMC #318917, is (NAPA #18-0397).  The later one from 1978 up to 1986, OMC #321387 which is they show as #18-2905, & which they call "water cover gasket" is the one that comes in the overhaul gasket set, not both as you would think if there was an overlap.  

 

In reality I have found #18-0397  that they call "thermostat gasket" is the proper one, which OMC calls "water cover gasket".  Also If you order #18-0112 that they call the "powerhead mounting gasket",  I have not been able to find where it goes on this motor, but in reality I  really wanted #18-2907 that they call an "adapter housing gasket" that OMC calls "powerhead to exhaust housing gasket".   So buyer beware!!!

One comment here on the electronic transistorized conversion kit.   I was at one time was quoted at about $60 for this unit.   Also from the experience of a marine dealer that says it does not work well if it is being used for trolling, as it appears the RPM is too low to give adequate ignition.

 

Also be prepared to pay the shipping & handling costs, with an average about $6.00 for a $23.42 gasket set.  Where if you ordered it from a marine dealer & it was shipped with his other parts orders, he may well equal out the shipping costs.

Listed below are some of the normally used parts found in the respective Marine Catalogs.  It is found that they both use the same part numbers.  The bold numbers are current prices as of 7-2004.

                   

Replacement Parts : The one online marine dealer that seems to have factory parts for most models is http://www.boats.net/ .  Their website has a online illustrated parts listing.  Their parts are discounted off retail prices.  They even have a parts technician that you can call to verify if you encounter any questions.   I am not sure how old of models that they carry parts for, but I had no problem getting water pump parts for a 1977 Mercury 4.5 hp.  They then ship FedEx.

 

The Internet & e-Bay can also be a source of new & used parts.  However, if you are on e-Bay, then you had better be darned sure that you are bidding on the right part, as many of these sellers do not know the fine details as to interchangeability & they must think that just because it is a 9.9 that everything else must also fit.  Or they read somewhere that all the water-pumps are the same, so assume that everything else is.   I have tried on occasion to inform some, only to be told I was wrong & to keep my nose out of their business.   As you have more than likely concluded after reading this article that it is NOT ONE SIZE FITS ALL, especially in the electronics.  

 

A few years ago, I bought engine parts off e-Bay that were advertised as fitting a  9.9, but the picture quality was poor, & after much research & comparison, it appears they may have been for a 1989  6 or 8hp instead.   Close only counts in horse shoes & hand grenades.

 

Back to OMC Info      Back to Ramblings

I am still learning about some things pertaining to these motors even after 30 years+, so information may change often.   And if I happen to answer a on-line question from a reader that I may have not thoroughly covered, many times I rewrite or add info & photos clarifying the issue.   I do wish to thank some of the e-Bay sellers from whom I borrowed some of the above motor pictures.

Copyright © 2004 - 2012 LeeRoy Wisner  All Rights Reserved

Originally stated 06-1998, Last Updated 01-28-2012
to contact the author click here