Maintaining Johnson 9.9 Troubleshooting

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

Maintaining Johnson/Evinrude 9.9 & 15 hp 2 cycle outboards

1974 – 1992 (Engine Troubleshooting)

I am sure that sometime you may acquire a motor, or be asked to help a friend with one that has sat for some time & or possibly will not start. This section will deal basically with getting a motor running, & not fine tuning it, as that is covered on the "Normal Repairs" article. Here will be my suggestions as to where to look & in the order generally accepted. You are going to have to have at least the 3 main things functioning for you, & they are all about equal in requirements. If the motor has an electric starter, we will cover that later, but for now, it is assumed on the first part of this section that the motor will pull over with the recoil starter, but will not start.

Has someone else tried to repair it & what did they do? If they did not know what they were doing, are the wires going to the right places? Are the ground wires making good connections? Is the motor just in need of TLC because of negligence on the previous owners lack of outboard motor maintenance knowledge?

Don't totally believe what the previous owner told you about the history of the motor. I purchased one motor that was supposed to have just quit. Usually this would mean that the problem would be spark related. When I got into it, there was dry, redish brown rust on the outsides of both coils, indicating that the motor had laid on it's side in water enough to get rusty. Compression was 62# & 105#. With the head off, it was evident that this motor had been immersed in water in some way. Maybe not dunked in the lake, but my guess in the bilge of a boat in the back yard without a cover & rainwater filled up enough to get into this motor. Both cylinders were hosts to LOTS of rusty & carbony oil. This excessive amount of oil could not have gotten there from inside the motor, it had to be squirted into the spark plug holes. There was also evidence of use of lots of starting fluid around the carburetor in apparent failed attempts to start it. The thermostat was missing also, & why is any ones guess. The electric starter was froze up. The lower unit had fish line around the prop shaft in front of the prop enough to cut the rear prop shaft seal out, there was NO oil in the gearcase & after flushing it with kerosene a couple of times there were metal filings & brown rust in the bottom of the drain bucket. The propshaft could not be pulled, in that the internals appeared to be effected by saltwater so the whole lower unit is scrap. The driveshaft was also frozen into the pinion gear & could not be removed. The trolling idle screw was missing. One clampscrew was almost there. The picture of this block with the head off is shown below. He had told an untruth & withheld many others in order to hopefully gain a little more in dollars in a transaction, & obviously the $200 that I paid for it was way too much. Don't take the word as gospel of a friend in buying of trading boat motors or horses.

These are all clues that you will have to consider in being a outboard motor detective. Sometimes the word "Detective" & "Mechanic" are closely related in cases like this.

For problems other than just getting it started, then read farther down in this section.

(1) General Appearance: Here you should generally get a real sense of what you will find as to the care, or non care the motor was subject to. Take a look at the overall motor, sometimes scratched paint can be deceptive, but if the owner had no pride in ownership even as to scratches, look farther. Pull the upper cowling off. Look underneath it for signs of oily residue. If the rings are bad, you very likely will see an oily film on the inside, especially near the carburetor intake as shown in the photo below.

Is the fuel line & bulb hard? If so you will need a new fuel line assembly. Beware of fuel tanks setting out in the weather. Are there any little kids around, if so check inside the fuel tank for rocks, sticks & mud.

With the shifting lever in neutral, give the twist grip handle a twist as if you were speeding up & slowing down the motor. If there is a lot of slop here, you may not be able to maintain a position without holding onto the handle all the time. With the older motors from 74 to 86 that utilize the gearing on the throttle shaft, this takes a lot of time to cut plastic shims & fir them to get proper tension if everything is worn. The 87 to 2006 cable throttle type are not usually prone to this problem.

You might find a gem that looks bad, but only needs spark plugs & clean fuel, but looks ragged, but the odds are not good in a case like this.

(2) Spark: Pull the spark plugs & look at them. If they have not been recently replaced, are they black & oily or just a gray color? They will usually be oily & possibly fouled since this motor uses an oil mix in the gasoline. You can clean them, & the best is with a sandblaster. Plugs are reasonably priced (about $1.50 each) & it may be beneficial to purchase a couple of sets. Then you can have a new set, & clean the others for spares. You might consider vacuum packing them if for longer dry storage. This will assure you that they are clean & dry when you to need to use them, especially if you are near saltwater. These motors seem to run best on Champion L77JC4's, than any other brand. Gap settings are .030.

You may be able to check for spark, by pulling the spark plug from the head, & reinserting it in the plug boot & then ground it, (holding the metal plug body against some metal part of the motor), while pulling the starter rope. You need to have made a good connection to the motor, (somewhere where the paint is not insulating your connection). You should be able to see a blue spark jump from the center electrode to the overarm on the plug's metal threaded area. It will not shock you, UNLESS you happen to touch the exact area of the spark jumping. This may be hard to see if you are alone & in bright daylight & have to pull the rope yourself AND look for the spark while the motor happens to be moving slightly. Here is where you may need the help of the wife or a fishing buddy.

If this is hard to see, you can make a simple spark jump tester as shown below, out of a piece of 1" X 3" X 6" wood, (2) 1/4" x 3 bolts & double nuts, a piece of aluminum, wood screw & wire with an alligator clamp on one end. Cut out 2 large holes & drill (2) 1/4" holes in the bottom center. Grind a tapered point of sorts on one end of each bolt. This tapered end goes up or the one that the spark will jump to the aluminum plate from. Thread one nut on the bolt push it thru the hole & place another nut on top, & when you get the distance you want, tighten the lower nut. The actual gap should be 7/16" to 1/2", but you can adjust it to what ever gap you want to the aluminum plate on top. Take an aluminum sheet & drill one hole in the center that will be used to attach the plate & the ground wire. Cut off the bolt head & deburr it so it will slide into the spark plug boot. You may want to use a black electricians tape or dark paper glued to the back side at the intended arc point so you can see the arc jump better.

In use pull the spark plug boots & position them on the 2 protruding bolt ends, clamp the alligator clamp onto an exposed bolt head. Pull the starter rope as if you were trying to start the motor. You should see the spark jump between BOTH the points to the strip for each cylinder. If it only jumps on one then you have a coil bad or possibly a bad ground connection at that coil, or even inside one of the rubber connectors or the spark plug boot.

If the motor is between a 1974 to 1976, the ignition system is the older points & condenser type. These coils & condensers can get weak over time, & may have spark, but a yellow instead of the hotter blue. Or the motor may start & run for a few minutes & then die. It will not usually restart for about 1/2 hr until the condenser cools down. What may be happening is that internally in the condenser (which is simply thin aluminum strips wrapped with waxed paper between them into a coil that is encapsulate into a metal container) the waxed paper may be slightly deteriorated & when the energy is created inside the canister, the aluminum expands slightly & where the paper is thin, will short out. After the aluminum strip cools, & pulls back the motor may restart. If this is the case you may need to replace the points & condensers, & even maybe the coils.

A test to try to get it running if the coils & condenser is getting tired, would be to reset the points to a larger gap. say .040, which will make the plug spark hotter & possibly firing it.

If you get intermittent cut out & die after the motor has run for a bit on a post 76 motor with electronic ignition, & you can not find the problem when doing your testing, try heating the powerpack up with a hair dryer with the motor running on the muffs and see if it repeats the problem which could be losing spark. It could be either the powerpack or the coil, so try both. Something is failing when it gets hot & this would be normal if total failure is just around the corner.

I had one motor that would not fire on one cylinder when it was cold, but after it ran a while the other cylinder would kick in & would then run OK. This is just opposite of what you would expect if a coil or electrical component was bad. I had changed plugs more than once, tightened the coil bolts, checked the high tension plug wires among other things & was about ready to tear my hair out. I even cut a fishing trip short by a few days because I did not want to get stranded in the bay with the wind blowing.

It was traced to #2 coil not having any output to the spark plug. I finally swapped coil input wires from the powerpack in the rubber connector boot, electronically changing the coils. The #2 plug now fired, but the plug wire from the old #1 coil was now dead. I then replaced the wires to original positions & replaced that #2 coil with another known good coil. Same results, no fire to #2 plug, so the original #2 coil was OK. This then was starting to point to the powerpack, but when they go they usually just die for both coils. It was getting late in the evening & I wanted to get the problem taken care of & with the motor still running, I just happened to look at the side of the powerhead, & there was blue arcing off the bottom powerpack bolt. Upon checking, I found the bolts holding the powerpack were loose & not creating a good enough ground. In my mind I knew it in all probability was a bad ground, but where & I would probably never have checked that bolt without seeing the arcing in the dim light. The good Lord does look out for us sometimes.

On the above motor after tightening all the ground wires, this motor still acted up as before. All the tests pointed to the powerpack. I bit the bullet & bought a new powerpack & problem solved. I suspect that since it took many fishing trips over a period of 6 months, thinking I had found the problem after each time, that one output wire or diode from the powerpack had become internally partially shorted.

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 illustration & 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)".

(3) Fuel: If the motor has sat for a while & just pumping the fuel primer bulb does not get the motor at least sputtering after you have concluded that the electronics are OK, have a squirt oil can with the proper gas to oil mix & try to start it by squirting fuel into the air intake of the carburetor as you pull the manual starter rope. Starting fluid will work, but don't overdo it as this has no lubrication qualities & could damage the motor if used extensively. A squirt or 2 of starting fluid into the air intake is plenty. It is better to use a plastic pump lever bottle with gasoline mix in it.

First to check would be is the fuel fresh & clean? If the tank could have sat outside or in a boat in the weather, there could be some leakage around the cap, or gauge. If any water is in with the gas, you will NOT have a smooth running motor, maybe even could not keep it running if you got it started. Now if you tried to start it with contaminated fuel, you have that bad fuel inside the carburetor, which will need to be torn apart & cleaned. It may be best to install a water separator filter system in the fuel line.

Second to check would be to whether fuel is coming to the motor. Is the fuel line connected to a VENTED tank. It works best if you hold the primer bulb upright, with the outlet upward. If the check valve spring is weak, this will help the pumping by not allowing the fuel to bypass & go back into the tank. The primer bulb should become hard after about 3 or 4 pumps when the carburetor bowl becomes full & the float valve stops the fuel from bypassing & being forced up into the carburetor flooding the motor. After the motor has run enough to remove this pressure of the internal fuel you have pumped, the bulb should become soft as the fuel flows thru it. A simple way to check if it he tank, pump bulb & line is functioning is to use a nail & push in the small metal ball on the motor end of the fuel line coupler. While you are holding this ball in, pump the primer bulb. If fuel gushes out this coupler & all over your hand, everything is OK up to there.

If the motor still fails to start & the suspect could be fuel, I would then replace the 3/16" fuel line from the fuel pump to the carburetor with a clear see thru line. You will be able to see fuel in this new line when you pump the fuel line bulb. This will give you an idea if the fuel pump is functioning. Matter of fact if I get any motor that appears to have a fuel problem, the first thing I do is replace this line with a clear see thru one. It has saved me lots of time trying to run down fuel related problems.

Have you removed the & cleaned the carburetor completely? If you frequent the outboard motor repair forums, the assumedly cure all for motors that do not run right if they have been setting for a year or so, is to tear it apart & clean/reassemble. This may not be the cure all, but it sure does not hurt to be sure the carburetor is free of rust. Normally if you are going to let the motor set for some time, you should run the motor enough after you disconnect the fuel line from the motor to where it uses all the fuel in the carburetor & dies. This then pretty well assures that the picture shown below does not happen. The one thing you do not know when you purchase gasoline, is just how free of water is it? Most all of the larger boats use a water separator filter system. But unless you live in an area where the fuel is known to be contaminated, these separators are hardly lever used in conjunction with small motors of the size we are covering here.

If there is any water in the bowl, it will usually block the main-jet & stop the motor from starting or at least make it run erratically. Rust will also do the same thing. Now if there is water in the fuel of the carburetor that has not been drained, the result can look like the picture below. You will note that on the newer motors, OMC did away with the metal bottom & replaced it with a form of plastic/nylon, which would eliminate this rust kind of problem. However you could still have the water problem.

If you do not know any history of the motor, then it may be best to suspect the worst. Usually you can tear the carburetor apart, clean it up, blow out as much as you can with compressed air & a simple reassemble with good results. However most of these carburetors have one or more small soft plugs that plug a hole that was drilled in the body to make air or fuel passages. If you blow everything out with air & the motor still doesn't want to fire or run properly, just maybe there is a blockage in these holes under a soft plug.

I recently ran into one motor that apparently had a watery grave, possibly during a flood because inside the carburetor, the main jet & the main jet passage tube were both plugged with a VERY FINE silt. I was able to remove the main jet & drill out the plug using the same size drill as the jet was made originally for. But then after having this carburetor off more times than I wish to remember, it finally hit me that possibly there was a blockage in the main jet tube under this soft plug (the only place I could not see thru). The price of a new soft plug was only $3.42 where the complete carburetor kit a mere $43.40. I ordered a new soft plug. But with fishing season approaching before it came, I removed the old soft plug by driving an ice pick into it & prying it out. Sure enough, the tube was as plugged almost solid as the main jet had been. On this model the tube had a slotted end down in the carb's body, indicating it may have been threaded in. However in trying to unscrew it, it soon became evident that I would ruin it before it came loose. So I straightened it best I could, & blew the tube out with high pressure compressed air. Now I can even see thru it. I peened the old soft plug slightly, reinstalled it & placed some JB Weld e-poxy over the hole I had made.

Before this it would have been totally impossible for fuel to get from the float bowl into the motor, that is why it would sputter when I squirted fuel into the choke area.

Another thing to look at is if you are running 2 motors off the same main tank, like say a 150 hp & a 10hp in all probability the large motor's fuel pump may well pull the fuel out of the small motors fuel line if the smaller motor is not running. Now when you try to start the small motor you have to pump the priming bulb for some time to bring fuel to the carburetor. You need to install a anti-siphon valve in the fuel line at the tank for the large motor. These are an economical small in-line check valve unit that has a threaded fitting on one end & a hose barb on the other end. You probably do not need to place one in each fuel line as the smaller motor's fuel pump should not be powerful enough to drain the other line.

If the preceding tests fail, then check the vent on your your fuel tank's cap. If you are using the old metal OMC tank, the cap is vented by the center screw head having slots cut under the head. This will automatically vent the tank unless these small square notches get plugged. The newer OMC plastic SysteMatch tanks I have not personally inspected, but from a picture it appears that they also need to have the vent screw backed out like the aftermarket tanks.

If you are using any of the newer or aftermarket plastic tanks, they all require you to unscrew the vent screw slightly. This need not be backed out to the point it may fall off, but just a part of a turn or so. If you do not vent the tank, the fuel pump will suck a vacuum & no more fuel can be pulled into the carburetor.

Check the fuel connectors to both the motor & the fuel tank. Sometimes they may pop off just enough to disconnect themselves but still be on the guide pin. The worst coupler to do this that I have found are the ones using a torsion spring wound around a central pin, with the tails putting pressure on the latch. Attwood makes a fuel line & coupler that uses a coil spring, which is quite a bit more secure than the torsion spring that Tempo uses. Make sure you have the fuel line on correctly, as it can be attached either way, but the check valves in the primer bulb will only work one way. On the bulb itself is an ARROW, indicating which way the fuel needs to flow from the tank to the motor. You will need to prime the motor, or pump gas from the tank into the carburetor. Squeeze the pump bulb, does it pump fuel into the carburetor? This bulb should pump up until it gets hard after about 3 to 6 squeezes. After the motor is running, this bulb will become somewhat less firm than it was initially when you primed the motor.

Pictured below is a dissected primer bulb. The red check valve assembly is towards the tank. These couplings/valves were dissected to show the internals. I swapped the red with the black plastic internal valves for better picture clarity. Normally the red will be with the red. Both valves use the same parts but different color, with the valve reversed in the outgoing one so that the fuel flow will go only one way. In the suction side, (red) it has a light spring pushing against the valve to prevent fuel from being pushed back into the tank.

If fuel starts running out of the carburetor when you pump the bulb, then you possibly have the carburetor float stuck our the needle valve may have dirt under it & may not be shutting off when the float reaches it high position. Also check for any possible fuel leakage at any of the fuel line fittings or at the fuel pump cover. On the older motors up until about 1990 or so that used the small fuel pump mounted on the RH side of the powerhead, there will be a large headed metal screw with a coin slot in it on the outside of the fuel pump. This can be loosened & the cover removed, revealing a stainless steel screen. Make sure this screen is not clogged, & that the neoprene gasket is intact & sealing properly. Also this plastic fuel pump inlet/screen cover can get cracked.

You could also have a crack internally in the tank's pickup tube, or gummed up gas plugging the tank intake. If it is sucking something up into or around the pickup screen the supply can be cut off, & when the motor dies, this debris can fall off & the motor may start & run again for a while.

If you pump the primer bulb & the engine dies, then you may need to look at the needle in the float needle & seat in the carburetor, as it may be leaking a bit, or the fuel pump is leaking. When all is well, pumping the primer will have not have an effect on the engine's running.

Another thing to look for that is many times overlooked, is the neoprene O-Ring on the inside of the fuel line connectors. These are inside the connector encompassed in a inner groove right at the outer end of the stainless steel shut-off ball. You will not be able to see how bad they are until you take it out. You can remove it by a SMALL screwdriver or ice pick. The are usually not strictly OMC priority & you can probably pick replacements up a at an automotive store or even a well stocked hardware store, by comparing to the old size that was removed. This size O-Ring is 14" ID with a 7/16" OD. If you can not find the exact same size, then opt for one that is the same OD but thicker. You may then have to grease this before you try to couple it to the motor or tank. These can get nicked or scratched just enough to not seal completely & being under a vacuum, can leak air & therefore not allow fuel to be sucked to the carburetor.

Check ALL fuel connections for leaks or cracks in the fuel line. I once found one that had a small crack UNDER the clamp & if you put the clamp back on exactly in the right place it would seal, but if it was slightly different location, then there was a vacuum leak on the suction side.

Check the gasket between the fuel pump & the powerhead. If this gasket got misplaced during a fuel pump inspection, you will have metal to metal contact & there will be a vacuum leak so the fuel pump will not function. This gasket is thicker than most, usually about 1/8" thick. I suspect it is so to insulate the fuel pump from the heat of the block & thereby prevent vapor lock when the motor warms up.

If you can pump the fuel line bulb when the motor hesitates, & it will resume running until the carburetor goes dry again, it is a good indication that the fuel pump is bad. You can easily check the fuel pump operation by removing the hose at the carburetor, pull the starter rope and see if gas comes out the hose while the motor is turning over.

Another method to determine if the fuel pump is bad without the engine running, unscrew it from the engine by the 2 screws and pump the primer bulb. If any gas comes out of the little vacuum hole on the back of it, then the diaphragm is ruptured.

These older small fuel pumps are rather cantankerous to work on & make them function. You may notice that the early ones do not show a repair kit for them. The later kits for this same small size pump will fit, it is just that the early bodies do not have the later style index tabs on them, so you need to be sure that the diaphragms go back the same as the originals were.

Also you may want to double check the fuel pump cover, as it being plastic, can become cracked & allow a gas leakage out, when you pump the bulb & air leakage will then break the vacuum of sucking the fuel in once the motor is running, at least until the carburetor runs dry. Both the above are detrimental to the engine performance/running.

If when starting, you can keep pumping the primer bulb & it does not become hard after about 3 or 4 pumps, & then fuel starts running out around the motor's lower cowling, the most likely thing wrong would be the carburetor's float needle valve is not shutting off when the bowl is full. The motor may well run, but could flood out if the fuel pump supplies more fuel than the motor can handle.

If the threads around the carburetor idle adjustment screw may have gotten sloppy, you can not get a true air/fuel mixture & the motor may run erratically. On these carburetors, there is a neoprene threaded gasket in the carburetor that acts as a seal. A repair kit has a new one, replace it when doing a repair job. If you are not doing a repair kit job & need to get a better seal, then you could smear some gasket maker or HEAVY chassis grease on & around the threads.

On thing also to consider how far are you trying to draw the fuel? Are you using the regular 5 or 6' fuel line attached to the 3 or 6 gallon portable tank, or have you lengthened the hose to 12' so as to position your tank farther forward in a smaller boat to balance your load better? This could also lead to hard starting of a cold engine if the fuel line vacuum has bled off .

Or are you connected to the boat's internal tank 10 -12' away, tee'd off to run both a large main motor & this smaller motor off the same tank? If running a single tank fitting & tee'd behind the tank, the main motor will usually have a more powerful fuel pump, & IF anywhere in the line system to the smaller motor may be defective, the larger motor may well be sucking your smaller motor's fuel line dry when the larger one is running. Now when you try to pump up the smaller motor's primer bulb, you pump till you get tired & it still does not pump up. You may have an airlock in that line & the only way to get it out is while you are pumping, push in on the ball at the motor's end, relieving the internal air & allowing the fuel to be hand pumped enough to fill the line, removing all the air bubbles. One suggestion here is to use a nail or something pushed in holding the ball down, while holding this line end high in the air when pumping, allowing all the air to escape. Then remove the nail & the line should be pretty full.

Another item to consider has the motor just been rebuilt & this is the first attempt to start it? If the reed valve plate gaskets are reversed, (the front put on the rear side) the gasket itself is a lot closer to the reed valve's exposed moving end & WILL stop the valve from opening. This in essence totally stops any fuel from getting into the engine. (Been there-doen that)

(4) Compression: Pull both spark plugs & check the compression. Open the throttle twist grip wide open to get an accurate PSI compression reading. Compression is not the only test you need to look at, but if taken into consideration with other factors it may well lead you to some conclusions as to the condition of the motor.

But don't be misled by just a somewhat high compression reading. Look at the photos below. Here the motor had been totally rebuilt with new rings about 30 hours before. The standard 50-1 gas/oil mix was used. The motor died & since it had an electric starter, was not noticed any differences except harder starting. Plugs were changed & it ran for a while. This time the lower plug had the electrode smashed flat against the center electrode. At the time it was thought that possibly the new plug was defective or that it had been dropped, deforming it. The motor was still running with about 4 more hours on it at the time it was taken out of service, but the bottom plug was fouled considerably.

Compression on this motor at the time it was taken out of service was 108# on the top cylinder & 105# on the bottom.

Miraculously, the cylinder wall was not scored badly & only a good honing job was required to clean it up. But the block got bulged & a hole about 1/8" was discovered on the RH #2 cylinder location just forward of the cylinder liner. This was cracked by aluminum piston pieces being sucked behind the piston thru the ports & then got poked out as the rod came around at the base of the cylinder. A clean up & wire-feed welding job remedied this problem. However this could have been probably been taken care of with a J-B Weld epoxy repair.

What amazes me is that even with the hole in the block & the broken ring/piston that this little motor still ran, not good , but it ran.

Here is evidence of the broken piston pieces being imbedded into the head	Here the blown piston, missing the top section of the lower LH ring groove. Note, the arrow pointing to the ring that has broken but stayed in place in the groove.

Use a good screw in type compression tester. You may encounter slightly different readings even when using 2 different testers, even if they are the same make & model. Twist the throttle handle to wide open to open the throttle plate to give it as much a chance as possible to breathe & allow optimum suction. Ground out both the plugs so as to not damage the electronics, or leave your spark tester hooked up. Pull it over as if you were trying to start it. You may get a difference of opinion here, but 3 pulls seems to be the norm. Do both cylinders with equalness in effort as to speed of your pulling & the length of the pull to assure that you are getting genuine readings. I like to pull it just far enough that I can feel the starter rope bottom out at the end of the stroke.

You will not find a recommended compression data from OMC, but they will say it needs to be about equal between the 2 cylinders, this being within 5# of each other. I have seen used motors seemingly run quite well at 75# & others that were a new rebuild at 125#. I would NOT like to see anything under the 85# however, especially if one was at 50# & the other cylinder was at 80# or 90#. This out of balance one would be a candidate for a re-ring job as the low reading cylinder very likely has a broken or seized ring. It would possibly be hard to start, & one plug would more than likely foul out often. I have seen some that run fairly well with a medium compression, but the rings or at least one is bad, however there could be fouled plugs or excessive smoking problems. The consensus from many boat mechanics is that if you have compression in excess of 110# on this series of used motor, that you have an exceptional motor.

If your testing shows low, then I would do 2 things, before I would get really dejected. First I would pull the head & look for evidence of carbon on the top of the piston. If carbon is there, then you may also have it in the rings also. This could seize the ring to the piston & cause it to not seal in the bore effectively, which can contribute to low compression. While the head is off, rotate the flywheel & look at the cylinder walls, are they scored or evidence of rust pitting? One thing to do when taking the head off, would be to mark which coil is the top one (this will be an invaluable help later). Another thing to remember for the pre 93 motors is that when you took the head off the 2 bottom bolts could not be taken out of the head while it was still in place because they hit the lower cowling. This means when you reinstall the head IF the powerhead is still on the motor, that you will have to insert these 2 bolts in their respective head holes BEFORE you slide the head in place.

The next step would be to remove the bypass cover on the LH side of the motor. With this cover off, you can see into the side of the powerhead & see the sides of parts of the piston & the rings, which will give you another clue as to what may be wrong. Are the rings stuck in the ring grooves, or is the piston grooves worn enough so that the rings wobble in the groove?

Look at the head gasket. Is there any sign of a non sealing surface between the head & the block. The head may be warped & need to be resurfaced. This can be done with a good file , but better by using a medium valve grinding compound on a old glass window. Place the compound on the glass & then place the head on top, apply downward pressure on the head & move it around on the glass with the compound, lapping it enough to take off any high spots.

Rusty/Carboned cylinders, 62# & 105# compression, not good.	Bypass cover removed showing pistons & rings thru holes, note top piston is pulled back to show rings	Scored pistons & very likely cylinders also, indicating seized or broken rings

The white color in the water jacket around the cylinders, top & bottom is salt deposit.	Note brownish rusty oil for top cylinder.	This motor was smoking excessively & using lots of gas

Since these motors are 2 cycle, & fire on the rise of the piston each time, it is crucial that the motor has GOOD compression on each stroke. You might therefore compare the compression on the first stroke & then against cranking it over another 3 or 4 times. By the nature of most compression testers, they allow a compounded poundage if cranked repeatedly. Just because you can come up with a higher compression by cranking it over more times, does not give you a true idea of the 2 stroke motor's capabilities & needs.

If the motor runs, but just doesn't seem to have the power & you have checked every thing else, try re-tightening the head bolts as you could have slight compression leakage. If this leakage has been there for a while & blown a hole, it will then need a new head gasket.

I have been communicating with one motor owner who is having lots of smoke coming from his motor when trolling & it uses LOTS of fuel, he says like an old V8 Ford. He has had it to mechanics & no one has narrowed down his problem. They are looking at leaks in his exhaust system for the smoke. His compression is 90 & 95#, the plugs are very oily but he has not had them foul to where the motor dies. My thoughts were that he has frozen rings in the pistons, or rings that have lost much of their tension & he is getting blow by. He later sent me the picture on the right above.

You would be amazed at how these motors can run at times while needing major internal repairs. Kind of like the Energizer Bunny.

OK, we have covered the 4 main items to look at. The following areas may be additional add on's of the above if you are still having problems.

(5) Flywheel Key Partially Sheared : Another check would be the flywheel key. If for some reason, the flywheel nut was not totally tight, and/or the motor had backfired, the flywheel key could have gotten partly sheared off. If this happens, the flywheel can get slid enough to throw the timing off enough to not allow it to start.

(6) Timing: One thing to check would be the flywheel key. If for some reason, the flywheel nut was not totally tight, or the motor backfired, the flywheel key could have gotten partly sheared off or rotated into a slight misalignment from the original setting. If this happens, the flywheel can get slid enough to throw the timing magnets off enough to create hard starting or possibly not allow it to even start.

This may not be as critical as the others, but worthwhile to check. The twist grip does have a position marked as "START". This is a position where the timing plate's cam positions the carburetor arm to where the ideal setting is for starting in relationship to the flywheel magnets & points or CD sensors. This cam plate setting should not normally have to be reset unless someone has tinkered with the motor, & they unknowingly may have changed this setting.

The throttle cam plate operates a cam roller that is attached to the carburetor. If this cam roller is cracked, broken or not functioning, it will throw the timing off. The throttle cam plate also rotates under the flywheel when you twist the twist grip. This cam plate has an arrow 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 earlier motors, you need the flywheel off, & loosen the 2 bolts on the RH side of the plate & adjust the cam plate to where it just aligns with the roller. To tell exactly when the shaft STARTS to move, take a small alligator clip & attach a 2" wire to the wire end of it. Clamp the clip onto the carburetor throttle shaft's Starboard side with the wire pointing UP. Twist the throttle until you see this wire pointer just move. The cam plate arrow should now be lined up. If not, loosen the 2 screws on the side & rotate the plate cam until it is aligned & retighten the screws.

Some mechanics like to set them so that the throttle arm JUST opens up a bit when this full neutral throttle is applied, I am incline to agree.
On the later motors the adjustment is different, (about 1986 or so) the timing cam plate that the carburetor roller engages is made of plastic with an adjustment screw on the rear (LH side) for fine tuning. The nature of this is that it is attached to the plate by a minimal amount of plastic on the front so the screw on the rear will allow it to move in or out for adjustment. If someone does not understand or they are poking around under the front of the flywheel they can break this plastic adjustment tail off. When this happens you will have throttle up to about 1/2 throttle, when the roller drops off the back of the broken part, the carburetor butterfly then drops back to an idle. It is usually hard to twist the speed control grip back to slow because the carburetor cam has now dropped behind this sharp broken off part.

In the photo below the red arrow shows there this cam part is broken. Normally the broken part will not be found & the owner does not know what is wrong or missing. With the twist grip at about an idle position as shown, you will see the black plastic carburetor cam roller against the cam & under the RH edge of the arrow.

(7) Timing Plate loose: This can be an item that may be overlooked, but it can be critical. Under the flywheel is what I call the timing plate assembly, this is essentially the whole charge coil/ignition module under the flywheel. It rotates when you twist the throttle twist grip. If the "Ignition plate to support bearing" (#47 ) or part #322435, becomes worn or warped, it will then be loose, this will allow the whole timing plate to rotate under the flywheel by the force of the flywheel magnets rotating around the coils mounted on the plate. This will cause the throttle timing to possibly change enough to create a non-starting motor. This support bearing puts tension on the inside of the timing plate dia. What usually happens is that someone oils everything up & this being one that gets a shot. It needs FRICTION not lubrication. You may be able to clean it up, then warm it in a micro wave & expand the ends to make it a larger dia.

This "bearing" is a fiber ring 5" in diameter, 3/16" thick & 1/4" wide. It is has a groove around in the inside to fit over the plate, & split in the middle like a set of piston ring to allow installation. If it is collapsed, meaning it has both ends almost together, it will not be able to put enough pressure on the timing plate. You may be able to put it in a micro-wave for a few seconds to soften it up, allowing you to spread it back out & be reusable. When installed it acts as a bushing excreting circular friction between upper plate & the block. The thickness up & down is not where the tension is put between the two but the outer circumference pressure.

There are 4 parts that constitute that this timing plate/stator assembly. First there is reference #41 or "timing plate retainer & link", next #46 is the "support plate" onto which is attached #47 bearing, ignition plate support" which is a plastic type large ring with a groove in the center. The outer edges of this plate #46 accepts #47 bearing. This bearing is made larger in diameter & has angled ends to be compressed & ride inside the #39 "timing plate & sleeve" unit that the stator is attached to. However it will not just slide on.

You will have to make a simple small wire staple that will hold the 2 ends in place while you slide #39 down over this #47 bearing. The best I have found is to place the bearing so the joint is pointing straight to the rear. Slide the timing plate assembly down & usually the staple will fall out, if not you can reach in with an ice pick & dislodge it from the bearing. Now it will fall on top of the block, so you can retrieve it with a small magnet. The red arrow in the photo below is pointing to the staple. The other bearing shown below is the position the normal bearing is extended. One is brown while the other is black, no difference, just possibly a different year.

(8) Throttle Twist Grip Functioning: It would be common however on the older cog gear throttle shaft linkage for wear to set in & there can be considerable slop in the twist grip settings. If this is so, never go from slow to fast to set it for starting, but from fast to slow. This can then position the timing a little faster & possibly set the carburetor at a slightly advanced position, giving a richer fuel mixture for the start situation.

Again for the early motors up to 1987, if the twist grip throttle handle (steering grip assembly) has developed enough slack that it is hard to find your position except if you move it from one way all the time. Or the engagement gears on the control gear & bushing assembly (#65) & the vertical shaft (#108) allow the gear teeth to jump out of mesh to where you may not be able to rotate the twist grip, you may need to make some shim spacers. These shims can be made from the plastic of the sides of milk jugs or other plastic bottles.

There is one screw (#62) on the underside of the twist handle that allows you to take the handle off. Be careful when reassembling the handle as there is a internal thrust spacer between the spring & the handle that has 2 protruding lugs that have to align with notches on the main arm. If you try to reassemble the twist handle & these mating thrust spacer notches are not aligned, you can not get the handle on far enough to get the screw in. You may need to twist things until the lugs engage, & then after they are, you may again need to twist the handle so that the screw in the shaft align with the hole in the handle. this screw. Be very careful that everything is square & properly positioned when you try to start the screw, as the shaft is aluminum & the screw is stainless. If it starts & goes in cross-threaded, it will just get tighter & to the point that it will not go all the way in. This can be a problem later, as the screw may not be able to be removed without breaking the plastic handle. If it does cross-thread, it may be wise to get a 12-28 tap & clean up the threads in the shaft.

If the throttle twist gears disengage, (#65 & 66) you may be able to place a spacer on the twist grip shaft between the end gear & the housing, pushing the shaft rearward. This can be performed without tearing any major parts of the motor apart. If this does not help & the gears still jump the teeth & get out of time, then it is time for a new shaft with the new gears, price of $46.70 for both it & the matching nylon bushing. You can weld new teeth back in or add bronze or silver solder to the tips to give more positive engagement. The newer parts have both bronze teeth as compared to sintered steel, nylon or aluminum for the older units.

The pivot nut (#83) (shown in the pictures in the #7 section below) is really only a jam nut locking the bolt it is threaded onto from rotating in the arm itself when the handle is raised or lowered. This bolt head is buried under the front bracket, which is threaded into the side of this bracket. To get to it you need to go under & in the channel behind the front plate bar. This bolt is again threaded into the base from the inside with not a lot of room to spare, so if you need to remove the handle you may need a 1/4" drive ratchet handle, appropriate socket & with a universal joint.

If the handle is just loose, to tighten it, you need to loosen this (#83) nut, then tighten the bolt to the desired tension & then retighten the nut against the outside of the tiller arm.

Now there seems to be one MAJOR problem with these models, and that is that the twist grip is not really designed to be operated in any other position above a 35 degree angle. If you tip it up farther & twist the throttle, you can experience these teeth to jump out of mesh 1 or 2 gear teeth without knowing what you just did. When in this condition, it will usually run, but at about only up to 1/2 throttle. It will not rev up to maximum speed as this flat will not allow complete shaft throttle movement.

When this happens, you may luck out by again raising the handle all the way up & twisting the handle back to SLOW, then moving the handle down & hopefully re-engage the teeth. There is a rubber cover on the top that does not allow you to see what has just happened. These gears at the handle pivot have one large flat on each, about the spacing of 2 gear teeth which have to mate, acting as a timing situation & main thrust function. When timed right these 2 wide gears should mate together in a position mostly in the upper position.

Farther inside is a vertical bevel gear (#109) that sits in the lower cowling is held in position by a separate plastic shaft (#107). To get to this you will need to unbolt the vertical control linkage shaft (#108} that goes into this lower gear & attaches on it's upper peg to the timing plate arm.

This bevel gear shaft (#107) has a hollow center in it & can be removed by simply forcing a medium sized screwdriver or 1/4" lag bolt into this hole, & then by twisting at the same time you raise the lag bolt, you can pull the shaft up & out of the lower gear. Mating into the gear #109 on the front is a horizontal gear (#52) that is connected to the front gear assembly (#65) by a intermediate shaft (#53) held in place by a snap ring (#67) onto #65 gear. These 2 bevel gears have a dot on one & a groove on the other which need to be aligned. In reassembling the intermediate shaft (#53) , to the gears, there are timing marks on all mating parts. The shaft has square ends, with one end having 2 small raised lumps, the other end has 3 small raised lumps. These lumps mate into matching small notches in the square holes in the gears.

If you get things out of time here, the mark on the twist handle will not align with the corresponding "SLOW", "SHIFT", "START", or "FAST' or positions.

If you have slack between the handle itself & the linkage for the throttle plate, then you can shim the bevel gear (#52) on the end of the intermediate shaft & the housing, pushing it rearward into a better mesh with the other bevel gear (#109). You may also have to shim under the other bevel gear (#109) (raising it) that is pivoted into the lower cowling. These last two jobs will have to be performed after the manual starter, vertical control shaft & vertical control shaft gear are removed.

(9) Has the Throttle Twist Grip Teeth Jumped a Tooth? : Check the twist grip to see that it has not jumped a tooth at the pivot point where the handle lifts up. If this is the case your indicator for START will not be in the right location relationship to the carburetor & timing. And if it does start it will not be able to run more than 1/2 throttle as the twist grip linkage will be off the one tooth.

DO NOT RAISE the handle very high & twist the throttle at the same time while you are running the motor unless you are prepared to disengage the gears, & change the twist grip timing relationship. This is explained in a subsequent section. Later, in about 1986 a throttle cable push/pull system was used to eliminate this problem.

You can check this by raising the handle & looking from the front at the mesh of the teeth on the 2 gears. One has a WIDE tooth that has to mesh with the other gear that is missing a tooth. If these teeth get out of mesh, about the easiest way to re-position them is to tip the handle as far rearward as possible, use a medium sized screwdriver & position the twist grip so it is aligned as best you can get it & then insert the screwdriver between the teeth & pry one tooth past the other & hope you do not break one off. The other method is to pull the twist grip off, tip the lever rearward, slide the shaft forward & realign the teeth & reinstall the retainer screw in the twist grip.

Gears in mesh	Gears out of mesh

Occasionally on the 86 & newer motors you may encounter one of the throttle 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 shown in the earlier section for this was passed on by a retired marine mechanic. His solution was to take a electricians #4 or #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 these models to place it on the cable beside the carburetor. Tighten the nut enough to just squeeze the cable inside the plastic sheath. Works like a charm.

#6 copper grounding clamp squeezing the cable on a 1992 motor, placed under the tiller handle & taped for exposure.	#4 copper grounding clamp squeezing the throttle cable on a 1994 motor

(10) Is it Running on Both Cylinders? : You might laugh at this question, but if it runs and has no power, is it running on both cylinders? You would be amazed at how good it may seem to run by just using muffs on just one cylinder & not in a tank or under power. I have even trolled all day long on just one cylinder firing. Here was a situation that after traveling for an hour to get to the bay, I had no high speed power, simply would not rev up. I knew there was a problem, & trolling with my 70 hp jet would be about impossible. I ran that 9.9 on one cylinder for 7 hours at a troll, not a smooth idle mind you but it ran.

The method of checking this is while it is running at a low or medium speed, pull one spark plug wire off, replace it & then pull the other. If it is running on just one cylinder it will die when you pull the wire that is firing.

If it is only running on one cylinder, there could be many possibilities, and I would look at them in the simplest order first (1) bad or fouled spark plug. (2) bad (loose or corroded) spark plug wire connections from the coil. (3) bad electrical connections (again loose or corroded) in the rubber plug-ins or wire leading to the coil. (4) bad ground wire connection (needs to be clean & with no paint where it touches the block under the coil. (5) the coil itself is bad. (6) leaky cylinder head gasket allowing compression leakage. (7) I have never seen a power pack on these 2 cylinder engines go dead for just one coil, (however it is possible, as have seen it happen on a 3 cylinder unit)

If you get to #6 & it is still dead, swap the coils from top to bottom & see if the non-firing follows the coil, if so then that coil is bad.

(11) Neutral Safety: (a) These motors are designed so that you CAN NOT start (by pulling the starter rope or engage the electric starter) the motor if the shift lever is in gear & the throttle is advanced beyond the start position. This interlock is operated by the shifting lever. The lever places the timing plate interlock so the throttle can not be placed in any speed faster than "START". Another interlock where the where he manual starter spool interlock ratchet teeth has a dog lever on the top, or the side (depending on the year) of the spool that drops down & engages a ratchet that prevents the starter rope from being pulled if it is in gear. 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.

(b) The timing plate interlock mentioned above blocks the movement of the timing plate until the shift lever is moved either into forward or reverse. It is supposed to be set so that the motor will start in either forward, neutral or reverse but only run at a restricted speed. If it is moved to forward, then maximum speed can be achieved. On the early motors, 1974 for sure, this interlock does not exist.

Some fishermen may disconnect or modify the above safety features if they use the motor for a back-up or emergency motor where every second may count.

For the electric start models there is another but hidden push button type switch that is connected in line so that the shifting lever has to be in neutral for the starter button to activate the starter itself.

On this 1987, manual start motor, note the shift lever in neutral & the black plastic Neutral Safety lever stopping the rotational movement of the metal timing plate arm at the center of the picture just below the center of the flywheel.	On this 1983, with the shift lever placed in forward, the metal Neutral Safety lever timing plate stop has dropped down, allowing the timing plate to over-ride the stop by minimal clearance giving full throttle movement. This timing plate is rotated by linkage to the twist grip throttle handle.

(12) Hard Starting When Cold : This may sound stupid, but have you actually pumped the fuel line primer bulb until it becomes hard, thereby pumping fuel into the carburetor? If you just start pulling the starter rope, you will have to pull it MANY times for the non-running motor to suck enough fuel into the carburetor to get it to start. Also we are assuming that you have already read & applied #2 pertaining to fuel in this article.

Some motors are finicky in that they may only require the choke be fully closed (knob all the way out) for possibly 2 pulls of the rope, then it be placed in the 1/2 way open position for other pulls, otherwise the motor may be flooded. Once it becomes flooded there is so much fuel in the cylinders & spark plugs are soaked that it may need to set for a while, or the rope pulled REPEATEDLY with the choke all the way in to get it to fire. Possibly you may even pull the spark plugs & clean or replace them. So you may have to get to know your motor's starting needs.

Also there could be wear in the twist throttle linkage, gears, etc. If this occurs, (which is common on the pre 87 motors) you might have to play with finding out just where the best position is for the twist grip to start the motor. Once you find this position, mark it as your new start location. Advance the twist grip to FAST & then bring it back to START to properly position the timing plate in the needed position to have it start. Some of these motors with a little wear in the linkage to the point where they don't advance the throttle at all until the twist throttle is rotated faster. Here the timing is being advanced, but the carburetor is not putting more fuel in to match the need.

Or if you have a post 87 motor, the cable linkage may be out of adjustment. This can be that the plastic ball coupler end on the cable needs to be screwed either in or out to be more compatible with the stators position. There is also a plastic threaded sleeve on the end of the cable sheathing that screws into the lower cowling pan, that may need adjustment.

The one most common problem with hard cold starting, if the motor is in reasonably good running condition, can probably be contributed to someone unfamiliar with motors & who just gets into the boat, pulls the starter rope & goes fishing. And the carburetor idle adjustments are not set for running but usually set more for trolling.

In actual use with the motor strictly set for lake trolling the fisherman 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 to your known trolling position later.

Getting into a worse case scenario which would require a rebuild, you may have worn piston skirts. If the skirts are wore it will not help pull fuel in when cold. Here you can have somewhat good compression but the engine has no vacuum to pull the fuel in. A warm piston expands some and makes a better seal on the skirt. You can usually start it by squirting fuel into the right side of the air intake (breather) to get it to start, & after it runs a while the metal may warm up, expand & possibly could be easier to start when then warm. Compression is related here, but does not relate totally because the rings are designed to seal from the top side of the piston. Compression could be acceptable but still not related as you are comparing vacuum on the carburetor side to piston compression on the head side. The reed valves could produce the exact same situation if they are bad & not seating.

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. This will usually be easy to detect in that it will make a mess under the flywheel, namely fuel/oil mix spilling down around the block. It is not impossible to remove & replace this upper seal without a complete teardown. However a simple somewhat fix is to pour a slight amount of STP around on top of this seal around the crankshaft. This oil is thick & sticky enough as to make a better vacuum seal.

(13) Bad Reed Valves : These are actually called Leaf Valves in the OMC parts books. If they are not seating properly, this could contribute to hard starting, BUT it would be one of the last things I would look at if the motor has not been recently worked on. If you suspect a problem with them, pull the air breather box off. With the engine running, look for blow back through the carburetor, it should be real noticeable at idle, as the carburetor should spit some fuel out the front.

In the picture below, apparently someone took it apart, & reinstalled the reed valves off set to one side on the bottom, leaving a gap as seen at the bottom arrow, creating a leakage for one set of valves. The upper one has what appears to be salt corrosion under the reed & the plate. These valves have to seat on the plate, (a good solid surface), no gaps, or corrosion. The thicker U shaped parts that have the screws thru them are the reed valve stops, so that the thin valves do not get deformed by being pulled inward beyond their limits. There appears to be some evidence of rust & possibly salt corrosion here. Neglected or possibly a dunked motor.

One thing here, you will never be able to salvage the gaskets on either side of this valve plate as seen in the photo, so you will need new gaskets, one against the block & the other on the manifold side.

Occasionally the possibility exists that a reed valve will break, when this happens the motor will not run very well & you should be able to hear a sucking noise from the carburetor at low speed it it will run that slow.

Also when rebuilding a motor, you may find that one reed valve may not lay flat to the plate. If this is the case look at the plate for straightness. If the gaskets were stuck tight & you had to hammer or pry this plate off the block, you may have bent it. If so simply lay it on a flat plate & using a hammer apply a slight amount of force in the proper location. Once it is bolted back down, it will usually then conform.

(14) Engines Revs, but Boat Does Not Move: Most logically this could be attributed to a spun hub in the prop. These props use no shear pin, & being a thru the hub exhaust, use a rubber bushing that is bonded both to the splined inner hub & the outer prop body. If for reason, (possibly hit something hard while running), this bond could be broken loose. It could be tight enough to hold for say a trolling speed, but if you rev it higher, then the hub may slip inside the bushing, causing something just like a clutch on an older car slipping.

This is easy to check, pull the prop off, look at the front of the prop and you can see the rubber hub between the inner metal splined hub & the prop body. Here, scribe a reference line on the metal spline & in line on the metal portion of the prop the hub sets in. Now put the prop back on the motor and go run it until the problem occurs again. Pull the prop back off and check the reference mark. If the marks are no longer in line, the hub spun.

These can be repaired by taking it to your marine dealer who will send it to a prop shop, as this is not really a do it yourself type of project. However on a small prop like this it might not be cost effective.

(15) Loud Clunking Noise at 1/2 Throttle Like it is Hitting Something. This could be the shifting dogs jumping out under power. These shifting dog teeth are pretty hefty & deep so this is usually not a problem. But if it is a motor that you do not personally know the history on, maybe in reassembly of the parts when doing a water pump repair, someone inadvertently screwed the shifting rod in or out of adjustment.

Pull the lower unit drain plug & see what the oil looks like, does it have any metal filings or ground up metal in it? Check the oil with a magnet. The shifting shaft link may be bent or need adjustment to keep it in gear if that is the case. Adjustment here needs to be done with how far you screw the shifting rod into the yoke of the lower unit when the lower unit is off the motor. Hold onto the shifting lever & see if when it does this jumping, do you feel the lever wanting to move at the same time the noise occurs?

I have also seen the forward edge of the clutch dog being worn slightly, this can cause the motor to jump out of gear on a heavy pull if the shifting rod is out of adjustment. A cure for this can be simply when you reassemble the lower unit, to swap the clutch dog 180 degrees front to rear. The dog slider gear is symmetrical & you have now just moved the worn forward dog to the reverse side where it will get a lot less use.

(16) Crankshaft Seals: Another area that can cause hard starting when cold is that the crankshaft seals can get worn & not allow suction from the back side of the pistons. If either the top seal or bottom crankshaft seals are bad, this could lower the suction enough to not allow the engine to start. The most likely of the 2 to go bad would be the top seal, because it will be more susceptible to moisture getting there under the flywheel & therefore rust on the crankshaft seal area. The flywheel itself being heavy & rotating could wear the top crankshaft bearing slightly, allowing the top seal to deteriorate or become worn. The actual determination that this is the problem may not be scientific, other than a somewhat sloppy flywheel side to side movement, but you could pour a slight amount of STP around on top of this seal around the crankshaft. This oil is thick & sticky enough as to make a better temporary vacuum seal. Other than that, a defective seal will be just a guess until it is actually removed. But the small price of the seal & minimal effort required to replace it could be a worthwhile guess after all the other tests & guesstimates have been expended.

This top seal is not that hard to replace as you do not have to remove the powerhead or split the case. This top seal can be removed by a seal puller, or by driving a self-starting sheetmetal screw into the seal enough to get thru the metal & then screwing it in deeper by 1/4" to get a better hold. Now you can get ahold of the screw with a pair of heavy duty side-cutting pliers & pry the seal up & out of the block. You may damage it enough on removal that you may not be able to even tell if it was defective. When it is out you can then check the crankshaft with a flashlight at the actual seal contact for rust. If it is bright, clean the block area & using a socket large enough to slide over the crankshaft & bear on the new seal, tap in down & into place.

For the bottom seal replacement, you would have to pull the powerhead & possibly split the case just as you would do a complete overhaul. Look at this as a last resort, but very seldom will this be the problem.

(167 Powerhead Seals & Gaskets: If there happens to be a leak around any of the mating surfaces of the block you can also get problems as being a 2 stroke, the crankcase acts as a compression / vacuum chamber & can decrease the efficiency of the motor. Check around the mating surfaces of the crank case for leaks. With the engine running, spray some WD40 around the possible cracks., if the engine picks up rpm, there is a leak in the mating surfaces.

(18) Bad Crankshaft Bearing Journals: If the motor has been dunked, or abused so that water has entered the block in any way, & not taken care of immediately, you could have a rusted bearing journal on the crankshaft. I have seen slightly tarnished journals that were in service with no indication of real failure yet. One had the lower rod bearing cap was rusted to the point that there was pits in it. It was obvious that this motor had seen internal water at some time, but had been run afterwards & was still running at the time of tear down. The reason for the tear down was worn rings, which may have also been caused by the water internally in the past as the cylinder walls were also stained, but not pitted.

This motor was put back into service with the same crankshaft but a polish job on the journals, new bearings & may even continue to run satisfactorily for the average fisherman.

(19) Twisted off Bolts During Impeller Replacement: This may happen when you try to separate the upper housing from the lower unit. If the 2 center bolts are the broken ones they are probably the least important ones & this hp of motor may well operate without them. However here is a method if repair other than a complete upper housing replacement.

The housing is aluminum & the bolts are stainless steel, not a good combination to remove in the 1/4" size. So first off try NOT to break the bolts. If a bolt does not want to unscrew without excessive force, try another & get a feel as to what it takes to break the bolt loose initially. Then go back to the stuck one & try again. If the bolt moves even slightly in a tightening direction, it probably is frozen & all you are doing is to twist the bolt. Not a good thing. In the photo below, the corrosion was between the lower unit hole & the bolt body itself, & not in the threaded section.

Here I use about a 3/32" drill bit & drill a hole in both of the housings where the bolt shank goes thru the lower unit AND into the upper housing where the bolt is threaded into. Drill in just until you hit the bolt. You may want to be sure you even go into the bolt ever so slightly, but just enough to open a channel into the threads. Put some penetrating oil into these holes. Tap the aluminum with a small hammer at this location. The purpose of this is to try to get some of this penetrating oil to get into the shaft & threads. The tapping may expand the aluminum slightly plus allow some of the oil to seep into the threads. Let it set for a couple of days. Tap some more, put more oil in the holes & try to unscrew the bolt. If after about 3 tries of this, & you still don't succeed, use an Oxygen/Acetyne torch & heat the area at the threads to where the paint is burned off. Put more penetrating oil in the holes & let it cool. Try to unscrew the bolt again. If it starts, then back it up to tight, then loosen it again to just slightly more than the first try. Keep tightening/loosening a little at a time until either the bolt unscrews, or breaks off. The oil holes can then be cleaned & an epoxy or body putty can be used to fill the holes, being sure that the threads are protected. Touch up paint is easier to do than breaking a bolt.

Now it would be best IF there is any bit of a stump of the bolt protruding to soak it with a penetrating oil repeatedly for a few days. Tap on this broken bolt as you soak it. Then try to get a ViseGrip plier onto what is protruding & slowly work it back & forth. if it does not move even slightly soak & tap again. If still no movement then heat the bolt with a torch as above, & while warm soak again with a penetrating oil. Note one of the best penetrating oils is common brake fluid.

Last resort would be to try & drill out the bolt & use an EasyOut, but most likely you could not get the drill to center within the bolt as stainless does not drill very well & doing it by hand, the drill will run off. Now when you have a hole partly in the bolt & partly in the aluminum housing & when you then try to unscrew it you may well break an EasyOut as you will be partly into the aluminum, binding the deal up.

A method I would use is to drill, roto-root with a Dremel Tool etc. to remove the broken bolt. You will now have to tip the motor upside down.
Make a template of the bolt pattern, (thin aluminum or heavy paper) mix up a epoxy, (JB Weld) & pretty much fill the gouged out hole. Spray a silicone onto the treads of new bolts & using the template to align the bolts & hold them in place & from tipping, insert the bolts doing a slight twisting motion to get the epoxy into the threads. Let it harden to about 80%, try to slightly unscrew the bolts just enough to break any bond that may have occurred. Let it set & when cured remove the bolts, file off any excess epoxy & reinstall.

One precaution here that may help someone at a later date would be to before you reassemble things to run a 1/4" X 20 TPI tap into each of these holes cleaning up the threads. Then when you reassemble the unit, place a dab of anti-seize compound on the threads.

(20) No Water Coming From the Overboard Water Indicator or Motor Getting Hot: This seems to be enough to place in an article all by itself. CLICK HERE

(21) Water Coming out Between Housings if Using Flush Muffs : When using the flushing muffs & a garden hose, you do not need to turn the water faucet valve on high, as it may be way more pressure than needed & can do possible internal damage to the powerhead IF there may be an unknown blockage.

When running the motor under these conditions, if there is water coming out around the shifting rod hole in the lower unit, as shown by arrow below, the following can be the problem. The rubber grommet on the outlet of the water pump, may not be inserted properly mating the pump housing to the copper tube that supplies the water from the pump up & into the bottom inlet into the powerhead. This grommet is held into the water pump housing by 2 ears & the tubing goes down inside it to form a seal. If someone replaced the water pump or impeller & was not careful when reassembling the lower unit to the midsection during final slide up & bolt together, the grommet can get slightly dislodged. You can not see this at the time of reassembly as it is not visible then. It may be not bad enough to harm water flow during regular running in the water, (you could not see it anyway as this would be submerged then) but when running from the flush muffs, & more hose pressure is on than normal, water can be forced out at this area around the shifting rod.

This may or may not be a problem. If the motor runs normal on the boat & shows no sign of overheating, there may a minimal concern. However if there is ANY indication of minimal water, a decreased flow coming out the pee-hole, or any indication of it running hotter than normal, then I would tear it down & refit the old grommet. Or, these grommets have underwent a design change making them more resistant to this problem happening. They have better retention ears, & are taller lending them to be more easier to become a slide fit covering more of the tube, for less of a chance to flop over. One thing I recommend is that you apply a slight amount of grease on both the tube & in the grommet to facilitate this blind assembly process.

(22) Engine Has Sat For a While : If the engine hasn't been used in quite awhile, very possibly with old 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.

(23) Engine is Seized & You Have no idea Why: Here you will have to do some detective work. Look over the outside of the block to ascertain if there is a broken connecting rod that may be protruding out a hole in the block. Put it in neutral & see if it still will not pull over. Try to rotate the prop, what you are trying to determine is that the problem is either in the powerhead or the gearcase. Can you rotate the flywheel any amount? There will be some slack in the bearings & connecting rods, but if it the pistons are froze up, it will not rotate more than a slight amount. If you get the flywheel to rotate a quarter turn or so, then it could be a broken rod.

It could be that the gearcase is seized up. This could be due to lack of gear oil, but usually it would be because a seal was leaking & water leaked in, then not used for some time, creating rust. If this motor was used in salt water, then usually the price of the bearings, & gears make the repair not worthwhile. You might be able to pick up a complete gearcase unit on eBay from a blown powerhead motor for less than 1/2 the price of repair parts.

Either way, you will probably need to (1) pull the lower unit as if you were going to replace the water pump. If you get the lower unit off & the motor will crank over, then you can be assured that the problem is in the lower unit & not the powerhead. (2) if pulling the manual starter will not allow the motor to turn over, pull the head, which may help give clues as to if it is in the powerhead area.

(24) Engine Has Been Hot & Seized : This will more than likely be caused by a non-functioning water pump, or something wrong with the cooling system. It could even be from a fouled carburetor or someone forgot to do a oil/fuel mix & the motor locked up. In this situation, the pistons more than likely have expanded due to excess heat & since the aluminum pistons expand more than the steel cylinders, the pistons can get seized in the cylinder bores. If the motor was running fast when this happened, the flywheel will be still rotating & will put a lot of torque on the rods & will usually break or badly bend a rod also. Many times the rod will break & the part still connected to the crankshaft is flying like a airplane prop & will blow a hole in side of the block.

If the block is OK & the rods survived, but the piston just seized in the bore, by pulling the head you should be able to decipher what has happened. If the cylinders are scored, it may be best to tear the powerhead down & check the pistons & rings & the actual condition of the cylinders. You may be able to just hone the cylinders to repair that damage. But at this point, since the unit is torn down, the cost of new rings would be low in my book. Buy a set & do the job right.

(25) Engine Has Been Dunked: Obviously this situation will need IMMEDIATE ATTENTION. You will have to pull the spark plugs immediately after recovery, pull the starter rope over enough blow any water that is inside the motor out. Spray WD-40 in the plug holes, crank it over numerous times & spray more WD-40 in. If it is fresh water, you will be able to clean the motor & salvage it. I would first pull the carburetor & clean all the water out of it. I would also recommend that you immerse it in denatured alcohol. This is so that the alcohol will absorb any water that you can not blow out with compressed air. The alcohol will then evaporate, taking the water with it. Without doing this you may have to run it for MANY hours at a not to successful situation trying to get the water out.

You will also have to look at the electrical system. There are rubber connectors on the wiring that should be disconnected & cleaned any water out of the connector holes. Use alcohol as a cleaner as it will absorb the water & then dry with no residue. If it is a motor prior to 1977, you had probably pull the flywheel & clean the points.

I would then place it in a large 55 gallon tank, as compared to muffs, as you will need to run it for many hours to dry thing out.. Then you can try to restart it. A few squirts of starting fluid into the air breather tube may make it jump into life, but don't overdue it as starting fluid has no lubrication qualities as compared to a mixed fuel. Mix a fuel oil mixture twice the normal ratio, like 25-1 as you need to lubricate the internal parts of this motor & that is the way a 2 stoke engine is lubricated on the pistons & internal bearings, is with the oil mixture with the gas. Once you get it running try to keep it running at a speed above idle, because you need to dry out the water & lubricate the internals. This is also a good time to after a few hours of running to adjust the carburetor for an idle.

I recovered one motor that had been dunked (not running) in freshwater for 2 weeks & it is now running fine.

(25-a) Engine Has Been Dunked in Saltwater: In a situation like this you will need to totally disassemble the motor & clean all the salt off SOON. And I mean TOTALLY disassemble it as if you were rebuilding it & do it ASAP, like within hours. The lower unit should have survived since it is sealed to keep the gear oil in.

(25-b) Engine Was Running When it Was Dunked: This will be a totally different situation, but will also require total disassembly, as that the motor will have sucked water into the carburetor, which may have built a something solid (water) inside the crankcase when the piston comes back on the fired stroke. Usually something will break inside the motor, & most likely it being a connecting rod. At very least the rod may become bent.

(26) What To Do if the Lower Unit is Dry of Oil: This can be a scary situation, especially if you just purchased the motor used from a friend/neighbor. Is it just out of oil, or is there any evidence of water in the gearcase? If it is just dry because of a leak? But usually if oil leaks out, then water can leak in. And if the motor was used in salt water, then the bearings could be damaged. Is the lower drain plug loose, or even VERY TIGHT? If it is real tight, then possibly the previous owner knew there was a leak somewhere, & he was trying to plug it by TIGHTENING this plug.

If the gearcase was dry, I would refill it with Kerosene, & crank the motor over in both forward & reverse gear if you can. If the motor runs, you might let it run with the Kerosene in the gearcase & in gear for a few minutes. Let it set for a few days & then crank it over again, then drain it out, catching the oil in a plastic margarine tub. Let this drained Kerosene set for a day & then carefully pour it off, leaving whatever residue there may be in the bottom of the tub. This residue will give you clues as to the internal condition of the gearcase. If it is just black sediment, you might be OK, but if it has metal filings or gritty gunk that is attracted to a magnet, then possibly the bearings are worn. This test will determine your next course of action as to whether you simply refill it with gear oil, replace the plug & filler screw plastic seal/washers & hope for the best, or you may have to actually tear it apart & see what is wrong.

On 1979 motor mentioned above & shown with all the oily, rusty pistons, it also had a BAD lower unit. No oil at all in the gearbox. After the Kerosene flush all I got was rusty brown gunk when drained. I could not even pull the prop shaft out of the housing with a puller (bent the puller). And the drive shaft was rusted so solidly into the pinion gear, that by even placing the shaft in my large lathe, & moving the carriage back to where it could apply pressure & someone else beating on the other side with a block & a 4# hammer, nothing would move. It is evident that there was probably saltwater inside it for some time. This whole lower unit is just scarp.

Another place to look for leakage is the prop shaft seals. If the motor happened to have monofilament fishing line wrapped around the shaft in front of the prop, it can be on so tight that it could have been forced into the seal, ruining it.

I have seen monofilament fishing line wound so tight around the prop shaft that you could start the motor in neutral, but when you tried to put it in gear, the motor could not overcome the friction at this low shifting speed & it would die.

The picture below shows that this mono got so hot that part of it molded itself into the seal recess, actually looking like it could have been the seal at one time.

(27) Electric Starter: We are assuming here that when you push the starter button that nothing happens, the starter motor does not engage & there is no noise from the starter at all. (A) Here, the number one check would be, are the battery cables properly connected to the battery? There will usually be some method of identifying the HOT from the GROUND wire, be it color, a ribbed grove, etc. If there is a RED color wire it goes on the Positive side of the battery. (B) Is the battery up to a full charge of 13 volts? (C) Check to see if the shifting lever is in neutral , as this activates the neutral safety switch & breaks contact to the starter. (D) Is the negative battery cable properly grounded to the motor's base? (E) Is the starter button itself functioning? (F) Is the starter free to spin? (G) Is the starter drive gear free to slide UP the shaft & engage the flywheel ring gear? (

Electrical diagram for manual starter motor	Electrical diagram for electric starter motor

Click on the above thumbnails for larger picture

Rust in this old metal carburetor bowl, not a good thing.