Johnson, Evinrude, OMC, outboard motor, outboard motor repair, outboard troubleshooting, 6 hp, water pump, carburetor,

What I have found is that most of these little motors under about 10 hp usually have lived a hard life.  They are used occasionally, run hard by a non-motor oriented person, hauled in the back of a pickup bed & then leaned in a barn corner until next time.  As an old horse trading days saying goes, "Run hard & put away wet".

I was in a Johnson / Evinrude shop the other day that has been around for some time getting my 2005 Evinrude E-Tec fuel injected 2 stroke motor serviced, (rather hard for us old timers when we can't work on a motor that requires a computer to make the adjustments).  Anyway I could not help but wondering thru their racks of used motors for sale.  I noticed of the motors here, there were about (5) Evinrude 6hp Fisherman & possibly (8 or 10)  9.9/15hp Johnsons making up about 1/2 of all motors from 2hp up to about 30hp that were there.

These 6 hp motors are relatively simple to work on, in the fact that about anyone with a little bit of mechanical ability can work on them & keep them running.  Those who shy away from the older points & condenser ignition system because they think they are obsolete & don't run very good, should try one of these when it is set up right.  After I have finished rebuilding the one in this article, it only takes one pull to start it no matter whether it is hot or cold.

Here I will mostly be dealing with a 1972 version Evinrude.   It seems that every used motor that I have ever bought from a private party has had something wrong with it.  Many times I purchased it from a person who never ran it & got it from someone else.   No matter who or what the circumstances, I seem to have to do repairs & some of them have gotten extensive.   It appears that most fishermen do not know how to maintain their motors, or maybe even do not care as long as it runs, somewhat. 

But I refuse to travel to a fishing area with a motor of an unknown quality, taking the chance of a potential problem.   Any used motor I repair has to run in a tank for a few hours at all speeds before I am convinced of their water cooling condition & carburetor idle jetting.   I even start then up the night before a trip to be sure they will be running when I am ready.   I am getting too old to have to crank & crank on a cantankerous motor or have to resort to a paddle to get back to the launch or worse just to a shore.   I have even called a couple of trips short by a day because of a motor that did not appear to be running right.  I have also stuck out a couple & had motor failures.

Similarities: In this series of motors, I am not as familiar with all the variations as I am with the 9.9/15s & have been fortunate enough to have a reader from Australia who has supplied some data that I was not aware of.  My thanks go to Noel Puzey. 

There are many similarities between the 5, 5.5, 6 & 7.5 hp motors of the years near the 1972 specified above.  Water pump impellers are the same for all from  2hp to the 7.5hp in years 1952 to 1978.  The 1979 impeller was an odd ball using a smaller diameter.  Some motors close in HP range used similar carburetors (either jetting or throat diameter), reed valves & intake manifold may have been changed also.   Some even used the same sized pistons, while others may have had a larger piston while sharing many other common parts.  Smart thinking by the manufacturer. 

Some of the following parts are shared by other size motors,  head gasket OEM # 329103 fits    5 HP 1965-1968,    5.5 HP 1959-1964, &   6 HP 1965-1979.  Gearcase seal kit   6 HP 1968-1979

At about 1978 the ignition was changed from points & condensers to electronic ignition (CDI) using a power pack & external coils like the 9.9/15hp used.  The later motors also started using more plastic parts than previously seen.

Points & Condensers:  The one good thing about them is that the points, condensers & some of the coils interchange from even the 2 & 3 hp clear up to the 40 hp motors of similar years, EXCEPT the 9.9/15 hp series which are different.   On these motors all the points are set at .020".   If you get a motor that is not firing, pull the flywheel (it uses a 3/4" socket for the nut) & clean up the points with a point file.   The last point file I purchased (2009) cost $7.50 from a auto parts dealer.  Sometimes all you are doing is to just remove oxidation off the contacts if the motor has sat for some time.   Most of the service manuals say to replace the points if worn or burned.  Well, take it from me you can clean them up for many more hours of run time.

Coils:  Coils for these points &condenser motors are the same from 1949 mostly up thru 1973 from motors 5.5hp thru 40hp.  The coils, especially those in the 1960's motors have a reputation for cracking and allowing moisture in and then starting to break down, creating problems.  The factory (or supplier) changed the plastic formulation on the coils at some stage and the replacement ones are considerably better.   About 60% of the older motors I have had, needed one or more coils replacing, and would be financially unviable for someone not working on their own old motor with the price of labor at $85 an hour.

Timing Plate:  If you have to remove this timing plate, there are 4 screws that need to be removed from the top that attach the timing plate to the timing plate base.  These screws are marked by the red arrows as shown below.  Note that 2 of them also hold the coils in place.   If you take it apart enough that the coils are loose, be sure that they settle down inside the small protrusions of the plate when you reassemble them.

Timing plate attachment screws

Recommended Spark Plugs: The recommended spark plug is a Champion J6C, however with a well used motor where the rings may be worn & oil foul  the spark plugs, some mechanics may recommend a move to a hotter plug, like the J8C.    And even open the plug gap up from the normal .035" to .045" which seems to allow the plug to run hotter & cleaner, especially for trolling.

Carburetor:  To remove the carburetor, you will need to disconnect the fuel line, the choke lever & low speed knob.  This knob just pulls off the finely splined shaft straight forward.  After that, you will have to then remove the two top bolts (using a 5/16" box wrench) from the recoil spool mounting plate.  Very carefully pull the complete starter to one side just so far that do not  pull the recoil spring out of the base.   You now have to remove the screw holding the carburetor cam linkage off the carburetor.  Now you can get a 7/16" wrench onto the LH carburetor mounting nut & remove that nut.   Replace the starter unit & bolt it back in to keep the spool & the spring from coming a nightmare.  Remove the RH carburetor nut, slide the carburetor forward off mounting studs. 

The carburetor is the basic simple standard unit & from about 1971 on the main-jet is a fixed one.  Earlier motors prior to about 1970 had an adjustable main-jet.  You will have to loosen & remove the rewind starter spool so you can get to the throttle lever pivot nut so you can then get a wrench on the port side carburetor nut.

You can usually tear the carburetor apart, soak it in a carburetor cleaner overnight, blow it out with compressed air & reassemble without purchasing a repair kit.  The float is varnished & may look cruddy, but if it is still intact & seems to float in gasoline it should function.  All that is usually needed is to check & see that the float level is with the bowel flange when assembled without the bottom bowl on & turned upside down.  If not parallel, then bend the metal stop tab on the float needle valve area to adjust the float level.  If the float is not set at the correct level for the shut off point under pressure from the fuel pump in the carburetor, this could cause motor to run lean or rich. 

Some carburetor repair kits cover a wide range of HP ranging from 5hp even up to 20 hp, however do not think just because the kit is the same for a 20hp as it is for the 6hp that they use the same carburetor.  The kits may have numerous extra parts, as main jets & you use the one required for your motor.  The breather throat may also be a larger diameter.

The main jet orifice in the bottom of the bowl has a recess on these models and be full of crud, even though they look clear.  On the later carburetors there is a clean out plug in front that you can access this orifice.   Use a proper fitting screwdriver to remove the orifice, & be sure there is no debris in or behind it.  Be sure the plug screw has a good sealing gasket.  This plug is in the same location that the early carbs had a adjustable main  jet.

Reinstall the idle/low speed jet needle & check the packing nut for tightness to insure there is no air leak around the shaft.   The correct way to adjust this low speed needle, is to turn it all the way in until it is lightly seated.  You then turn it back out 1  1/2 turns.  That becomes a reference point for further adjustment.  With the motor warmed up & the twist throttle in a SLOW position approximating your intended slow/trolling speed, turn this low speed needle jet in about 1/8 of a turn, let the engine run for about 15 seconds to respond to your new setting.  Do it again & wait for the results.  When you make this change & the engines either sputters or wants to die, back it off the the last position & this should be close to the ideal setting.   You can now pull the idle knob forward & off the splined shaft, reposition it so that the knob pointer is down & you will have movement either way from this position for fine tuning if needed.  This low speed setting does not effect the high speed running of the motor.

One thing if you look at the top of this carburetor, the 1/8" hole at mid-section topish is not plugged with a lead shot like all the rest.  My thinking was did I loosen it & loose the plug?  Well, after I got it running I covered that hole with my finger & the motor wanted to die.  After numerous tries, I decided it was not supposed to be plugged anyway & probably there as a vent to alleviate any vacuum inside the float bowl.

There is no breather on this motor as the mouth of the carburetor is open behind the front of the cowling.

The later (1980 on) 6hp and 8hp are identical with inlet manifold/reed valves/carb throat size being the differences in hp.  Much of the motor is similar to the earlier 6hp version but parts are not interchangeable in the main (different head, possibly same block).

Starboard side view of carburetor showing the idle jet shaft & choke rod.

These motors are all new enough (made after 1959) & used the single fuel line commonly found nowdays.   And these fuel pumps are pretty universal, the same one fitting most all these small motors up to 40 hp until about 1987.

Recommended Fuel / Oil Mix: Fuel/oil mix on all the OMC motors that have needle roller bearings is 50-1 of TCW-3 standard outboard oil.  However I have found that since I troll much of the time, other than getting there & back, I like to use a mix of 75-1 but of a SYNTHETIC blend oil instead of the standard oil.  This gives me better motor lubrication, plus it gives me less smoke at a troll & the spark plugs last longer before fouling.

To Start It:  These points & condenser motors when cold usually won't start in the minimum throttle position until you advance the throttle twist grip to line up with the "start" on the sticker at the base of the throttle grip.   If in doubt if the markings have disappeared, then advance it to about a medium/fast setting as it will start if set faster, but will NOT start if set lower.   Pump up the fuel line primer bulb until it becomes hard.  Pull the choke knob out & with a quick effort pull the starter rope.  If everything is functioning, it should start, possibly on the first pull, but usually within the first 3 pulls.

Low Speed Stop Screw:  The later CDI electronics motors have an adjustable stop screw on the bottom gear at the end of the rod that moves the advance mechanism (base of the handle).

To Stop It:  There is no kill button on these motors up to about 1979, you just retard the throttle twist grip as far clockwise as it will go & the motor should die, it not, then choke it to kill it.   At 1979 there was a kill button located below the idle adjustment knob on the front cowling.

Problems: On the motor I was working on, after trying to start it, then checking spark (or non spark for one cylinder), then when I got this motor together enough to run, it had more problems, which appeared to be timing & carburetion issues.  The timing plate was so loose on the pivot post of the block that it wobbled every time the flywheel rotated & the flywheel magnet came close to a coil. 

In my junk box (before I cleaned the shop & sold the aluminum scrap) I found a timing plate assembly off a older QD 10hp with the coils, points & condensers still attached.  They looked very similar, WHAT THE HECK, presto the plate measured the same & even fit the pivot post a lot tighter than the one I took off.  There were items like the timing cam plate & throttle linkage pivot that were different, but once these were removed the others off the 6hp bolted on with one difference.  The only real difference was the mounting holes for the timing cam plate.  The 10hp was rotated to the right one bolt hole.  However there was no hole or threads there for one end of the 6hp timing cam.  The casting boss was there, being cast into the base.  I drilled & tapped a #10-24 hole centered in the blank boss & we were off running.

Modifications to Timing Plate: In the LH photo below shows the original 6 hp timing plate.  The 2 threaded screw holes are as needed.  The 10hp plate needed a new hole & threads at the BLUE arrow.  Then the timing cam was simply shifted to those 2 holes & the RED arrow hole was abandoned.

I used the 10hp points, (they were better than mine), the same condensers & coils off the 10hp also.

Bottom side of timing plate	Top of timing plate showing ignition system

The throttle cam, at least on this 1972 version was just a plain plastic post.  The newer ones (at least in the 1978 parts catalog) show a roller on top.  I understand why, as this solid plastic cam had 1/16" wear at the timing cam mating surface,  (possibly because of the loose timing plate) creating a initial timing problem.  I did a patch repair using 4 minute J_B Weld epoxy, filling the worn hole.   In looking at the factory service manual for this model they recommend lubricating this mating surface between the lever & cam.

Recoil Starter: The recoil starter uses a rope type spool system that works very much like an automotive type starter unit only manually.   The service manual says if you have to replace the rope do it with one 56 1/4" long.

Port side view of the spool type starter

No Overboard Water Indicator: The motor I was working on did not have a overboard water indicator (pee hole) which would probably not came into being until about 1978 if things follow thru as with the 9.9s progression.   I have looked at other newer motors & their indicator line comes off the sideplate cover.  However 3 of my sideplate bolts were seized & 2 of those were in a hard place to get to at the bottom & the chance of twisting them off was not to my liking.   Plus I did not really want to tear the powerhead off the midsection to get to the possible twisted off bolts for repair.

Time now for Plan B, I have traced the water flow in the service manual & found that a simple modification to the thermostat cover can be made to create a pee hole line.   The thermostat cover is at the top rear of the head.  It uses 3 bolts for attachment.  There is a bypass flow from the intake to behind the thermostat. 

Water passage thru this motor

If you take this thermostat cover off & Heliarc weld a slight amount of weld (even using JB Weld epoxy would work) on the top side at the same location that the bypass enters from underneath, you can then drill & tap for a 1/8" pipe tap, USING THE BYPASS HOLE ON THE UNDERSIDE AS AN ALIGNMENT GUIDE.  DRILL FROM THE UNDERSIDE, CENTERED IN THE EXISTING ROUND RECESS.  You need to add this material because the cover is so thin as that location that you possibly can not get enough material to give more than a couple threads for the Ell.  Now you can screw a 90 degree pipe elbow (it is best to purchase an OMC plastic barbed Ell made for this) into this hole & add rubber tubing to the starboard side & drill a hole in the lower rear cowling for it to exit.

Location of the new fitting on the top side of the thermostat housing cover	Location of the new fitting showing the threaded Ell on the bottom inside of the thermostat housing cover using the existing water channel entrance as a drill location

Unforeseen Problem After Overboard Water Conversion: One thing I found after this project was done was that now the upper cowling would not seat far enough down for the to latch to function.  It appears that this Ell now just happens to sit exactly under one of the 1/4" bolts that attach the lifting lip to the motor cover cowling.  However if you purchase a 1/4"X 20TPI  X 3/4" FLATHEAD stainless steel bolt & countersink the fiberglas at the hole to accept the taper under the flat head, you will just have enough room for clearance.

Rear view of the placement of new pee hole elbow & line on the top of the thermostat housing	Note the new countersunk flathead screw on the left needed for clearance of the new Ell fitting.

Water Pump Repair: This water pump & gearcase is very similar to the other OMC motors up to & including the 9.5, 10, 15 & 18hp motors made up until about 1973.

The water pump impeller replace job is a simple remove 4 bolts at the lower unit to mid housing.  Shift into reverse & the lower unit drops down enough to remove the bolt from the shifting lever coupler as normally encountered.  Different than most however, the service manual says rotate the engine (by either using the flywheel or prop) to align the dowel pin in a slot in the upper mid-section.  Presto when it aligns up inside, the whole lower unit & drive shaft comes out like all the others do.

Water pumps are basically the same design as still used on all outboard motors.  These impellers are a larger diameter than on some of the later unitized lower units, in my book they appear to be able to still function even after many years of usage even after becoming less flexible.  The one thing the early units, (as with this one) was the pot-metal cast housing & was in normal deteriorated condition being well worn inside.  It is then recommended to replace the pump unit with the newer stainless steel liner version if you have plans on keeping this motor in your stable for some time.

The exploded views in the service manual (shown below) show a gasket, seal, spring & washer at the upper part of the driveshaft.  I suspect that it is for the lower crankshaft & when the driveshaft is pushed all the way up into the crankshaft splines, the dowel pin in the driveshaft then pushes these all together.  Rather odd arrangement, but as of yet I have not removed the powerhead to verify.

Water pump & drive shaft exploded detail taken from 1972 OMC service manual

Below is a photo of the older style water pump housing used on this motor that does not have the stainless steel inset.  Note that there is wear on both the top & bottom plates.  This particular pump did not function very well.  Matter of fact it pumped water so sporadically that I modified the the motor to a newer pee hole style because I was unsure as to the real condition of the pump.  I suspect there was just enough wear on both sides of the impeller that it was bypassing water somewhat.  Also inside the impeller housing in one location were 2 small holes about the side of a matchstick.  Behind them were indications that they had also worn the impeller. 

The newer motors at about 1978 used a nylon water pump housing and stainless steel  impeller liner which is far better than the original metal water pump pot metal housing. This new housing can be retrofitted to the older motors.  The 1979 water pump used a smaller impeller diameter.

Some might call me frugal & from my scavenging listed above, maybe so,  but with the price of a new pump unit at over $46 & this being an old motor of unknown qualities, I did not want to invest a bunch of money before I found out how it eventually may or may not run.  Being retired & on a fixed income also could have been somewhat of a determining factor.

Pawing thru my junk box again, I found water pump parts of a older QD-19 10hp.  The stainless base was the same exact size & shape as the 6hp only better condition.  The housing was the same only the center hole indicated a larger drive shaft was used, it however was in worse shape than the one I took off.  

Original worn water pump housing & plate

I salvaged the 10hp bottom plate & placed the existing 6 hp housing in my metal lathe.  Mind you that one of my professions in the journey of life was a machinist.  Dial indicated it square with the jaws, I then reached inside with a boring bar & removed about .008" off the unworn center (just enough to clean it up) to match the wear of the impeller vanes being careful not to take to much because the impeller hole is now eccentric to the lathe chuck.  Then I removed about .015" off the bottom flange to compensate for any possible wear & what I removed.  Hopefully the new impeller would be a tight fit like originally designed.

I then mixed up some JB Weld & filled the 2 holes.  Later I sanded them down matching the rest of the inside housing & cleaned up the non-wear behind the holes.

A new water pump outlet grommet that I had left over from a previous 9.9hp repair (same grommet) was installed before final assembly.

Water pump being reassembled, note the protruding shifting rod	Water pump assembled, showing water outlet tube

Water Pump Re-Assembly: I have found it best to inset the impeller into the housing with the ears rotated as if the motor was being rotated clockwise looking from the top.  I usually lubricate the vanes with a slight amount of oil.   Slide the housing & the impeller down the driveshaft.   Be sure to place the impeller key in the shaft & slide the housing farther down onto the key.  This key is made in the from of a Tee.  The bottom beg is rounded that goes into a hole in the driveshaft, leaving the top of the tee which is rectangular slide into the square notch in the impeller.  It wants to turn sideways slightly enough during assembly that you need to have it very close as the 2 slide together to assure it is right.  Bolt the housing down to the lower unit base.

Upon reassembly, the only thing different than the normal water pump reassemble was that of lining up the 1/8" dowel pin in the driveshaft upper section with the slot in the midsection just below the powerhead.  You can shine a flashlight up the housing & see what needs to be done to align the dowel.  As you align the driveshaft, you also have to align the water pump tube in the mid-section into the water pump outlet grommet.

Shift the lever into reverse & pull the lower unit shifter shaft UP, so the shift linkage coupler can be aligned & screwed together using the coupler. 

The water supply tube to the motor from the water pump is a short 10" slightly bent shape seen in the photo above.  This tube may come out of the upper grommet upon disassembly.  If it does, replace it in to that upper grommet before you try to slide everything back together.  It is about impossible to align this tube to the upper grommet AND get the shift coupler AND the driveshaft rotated right all at the same time unless you do it this way.  Doing it this way using a flashlight if needed, the tube & lower grommet coming out of the water pump housing, & the shifting coupler can all be seen at the same time at assembly.

One bit of advise, use one of those mechanics flexible shaft fingered pick-up tools to place the coupler screw in the coupler because now you have a narrow space about the size of the head of the screw, between the mid section & lower unit & if you drop it into the lower unit cavity, you have to pull it back apart & shake the screw out to start over.  Then a good fitting screwdriver can finish the job.

Motor being re-assembled, arrow showing shift linkage coupler screw after the 2 rods are connected

Thermostats: These are the same from 5hp to 55hp for years 1959 to 1994.   Since these motors are usually used in fresh water only, they can usually be removed & cleaned up with no problems.  Do not run a motor without the thermostat as the motor will not run in a high enough temperature range to allow the motor operate at it's efficiency level, plus if you troll it a lot the spark plugs will foul a lot because they are not up to a proper operating temperature.

Driveshaft Changes: There were a number of detail changes over the years from 81 to 90 with different drive-shafts and crankshafts (the number of splines change, approx 3/4" change in the length of the shaft etc) which make it a pain to work on as different year parts may fit but may not.

Long Shafts:  Long shaft motors were available.   The difference being the water tube and driveshaft length and a longer exhaust housing based shifting rod and the extension.   One advantage over the 9.9/15hp is you only have to remove the 4 lower bolts on the extension housing to remove the gearbox - just like the short shaft - not both sets like the 9.9/15 to access the shifting rod coupler.

Observation: One reader from Australia has found through experience that running these motors in a stationary test tank may not always produce a great flow of water through the cooling system -- they require the forward motion of the boat plus the prop rotation to help send water to the pump.   However in my test tank I have no problem in this matter even at an idle if the motor is in forward gear. 

Shift Lever Breakage: A common problem is a broken pot-metal gearshift lever.   The motor falls on its side and this breaks where the steel shaft is molded to the alloy shift handle.  A pain to fix usually unless you know a good aluminum alloy welder.  The shifting lever rod runs through the exhaust so the little cam that transfers motion from the lever to the rod corrodes and it is just about impossible to remove the screw without damage.  A new shift lever is expensive, and of course you have to remove the powerhead to access it.

Shift Lever Stops: The positive click stops for the shifting lever is by a Ell shaped bent spring that snaps into notches on the shifting rod inside the lower unit.   This spring & a helper spring are screwed into the lower unit above the prop shaft & mate into notches in the shifting rod.  This motor's stops were non-functioning.  However what I found was that the spring & helper were there & OK, just that they had gotten slid forward enough to not engage into the rod's notches.  So it was just a simple matter of realigning them & retightening the screw.

Twist Grip Problems: The twist grip retainer screw threads can become cross threaded upon reassembly if you are not careful.  About the only way to correct this is to run a 12 X 28 (this is an uncommon, but standard size) tap thru & clean up the old threads.  Then be very careful when you try to get this screw started because the handle is under spring tension.  I have found that it is best to get the threads aligned with the hole in the handle as best you can while holding the handle rearward as tight as possible AND then using a small Philips screwdriver or similar tool to reach in thru the handle hole & try to align both while holding tight.  Then get the screw started as straight as possible.

These motors DO NOT share all the same problematic throttle twist grip gearing system as mentioned extensively in the 9.9 articles,  in that these series you can raise the handle up while changing speed without jumping the gear teeth.  This one used the early gears made of cast bronze, I had to braze new teeth onto the broken ones & hand grind them with a Dermel tool to match the originals. 

Tilt Lock: This motor has a lever lock in front under & behind the clamping screws to hold it in the running position, but not have a tilt lock to hold it up, only a nut on the end of the pivot shaft that is a tightened so that the motor will stay up while yet being able to be tipped back into the water without a lot of effort.

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. 

Motor Mounts: The rubber motor mounts are pretty well designed, a rubber block with attachment bolts molded into them last a long time & are externally mounted.

Cowling Change: There was also a cowling change approx 1975 where the aluminum lower cowling had a straight upper edge with a matching straight lower edge on the fiberglas cowling.  The pre 75 cowlings are not interchangeable with the later ones.

Prop: The prop uses a shear pin 3/16" (.187") diameter X 1.380" overall length.  These pins appear to pretty substantial & I doubt if they would break before a blade on the prop.  This motor uses a 3 blade prop in  8 1/2" X 5 size & has a 9/16" prop shaft hole.  There are 2 blade and 3 blade props for these motors with differing numbers but they all seem to work well.

The prop on this one is a metal filled plastic of sorts & must have been abused as it is now only 7" in dia.  

Once the hp of these motors gets over 7 1/2 hp the prop shaft increases in size to 5/8" so any interchange of used props over that is not possible

This particular motor also had a broken tiller handle that after searching e-Bay for a while I acquired a replacement, hence the different color on the photo below.

Motor in running condition	Same motor after a paint job
	As soon as I get this project finished

Originally stated 06-03-2009, Last Updated 06-17-2010 
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