Lower Unit

ohnson, Evinrude, OMC, outboard motor, outboard motor repair, 9.9, 15 hp, year of manufacture, powerhead, piston, water pump, carburetor, long shaft, 15 hp conversion, sailmaster

Actual Removal of Gearcase to Access the Water Pump: If the motor has been used in saltwater to any degree, I will guarantee that at least a few of the bolts will be seized in & will be twisted off. I will cover this in the troubleshooting section however. Have the motor mounted either on the transom of the boat, on a motor stand or saw horses. It also will make a slight difference in the procedure whether the motor is a long shaft or not. There are 6 stainless, 1/4” bolts with 3/8” heads that come in from the bottom & are bolted up into the exhaust housing assembly. If it is a short shaft, they are the only ones there. If however it happens to be a longshaft, there is a 5” extension, or if a Sailmaster a 10" extra long extension between the lower unit & this housing. If so, then remove the upper 6 bolts for access to the shift linkage coupler. The lower 6 bolts attach this extension to the lower unit which would need to also be removed to access the water pump.

When you get these 6 bolts removed, the gear case unit should drop down about 1/2”. If it does not you may have to tap it with a plastic mallet. Shift the gearshift into forward. When the lower unit does slide down, there will be, inside the housing in the front right hand side, a connector that is a strap with 2, ¼” holes top & bottom & 2 bolts that are screwed in sideways. These bolts go in a circular groove of the shifting rods, & hold it in place. Remove only the top screw. It has a hex head & also a screwdriver slot. Once this bolt is removed the gear case unit can be moved downward & off.

Clean Out & be Sure the Front Cavity & Drain is Clear: When you get the lower unit separated from the midsection look at the large forward cavity in the gear case unit. This cavity is only accessible from the top when the gear case is removed. This cavity has a drain hole coming out just above & on the left hand side of the rounded gearcase boss. If the motor has been used near saltwater, this whole inner cavity can become plugged with salt/aluminum corrosion residue. The shifting rod runs down into the gear case in the middle of this cavity. Do not remove this shifting rod at this time, as it has a rubber O-Ring seal around the lower end to keep the water out. If you unscrew this shaft & take it out before you clean this cavity, salt & debris will fall inside the gearbox. And you might have problems getting the threaded end of the shaft aligned back so that it will start into the threads of the shifting yoke inside the lower unit.

You may have to use a long screwdriver or something similar to dig out much of this debris. This salt/aluminum debris can be packed in very hard. Wash it out & keep digging, as there is quite a large cavity here. The internal drain hole to the outside drain hole is in the very forward part of this triangle. You will also need to weld a 1/4" extension on a standard 3/16” drill bit that will be about 9" overall. Use it on a drill motor to drill out this crap, especially down to the drain hole.

For the older motors, you will then need an 1/8" drill to clean out from the outside hole into the inner cavity, location as shown by the arrow in the LH photo below. On the later motors of late 1980's on this hole was increased to 1/4". When you get this cavity clean, wash it out with water, & observe whether the water runs out the outer drain hole.

In the RH photo below, the water pump housing is what you see attached by the 4 bolts. The arrow is pointing to the shifting rod coupler visible on the small shaft.

Drain hole for the cavity from the outside	This is what it should look like.

As you can see from the LH photo below, the housing is cracked & even a chunk of the outer housing missing. This in itself may not effect the operation of the motor because inside this particular area is just a void & not into the gearbox itself, UNLESS there are other internal corrosion possibly into the gearcase. The small round hole is the drain hole shown in the previous photo above. RH lower photo, unburned gas/oil from excess idling during trolling PLUS salt corrosion accumulated here. If the drain hole was clear, this oil would drain out & not allow this much build-up.

You may think that since you flush your motor that with muffs each time, that this cleans this inside cavity as well. Not for this cavity. If the cavity & corresponding drain hole is clear, when you remove the motor from the water, about ½ a cup of water should run out this outer drain hole. When removal from the water, this can drain water out for a couple of minutes. It is recommended that you find a small nozzle & back-flush water into the outer drain hole each time you flush the motor. The later models increased hole size to about 1/4" & it would be recommended that you also do this, in that the factory must have decided the smaller hole may have been detrimental as shown by the 2 photos above.

Another thing you may encounter is corrosion devouring the aluminum at the water pump base. If the aluminum (usually in the front) of the base under the water pump is deteriorated, you can clean it up by sandblasting & then build it up with the epoxy called J-B Weld. There has to be material there otherwise the flow of water being sucked up thru the intake screens & then into the housing below the bottom of the water pump will not direct the water in the right place. This can then greatly effect the efficiency of the water pump.

Shown below is a cure for this corroded area. Lathe turn a stub shaft that just goes into the shaft seals on the bottom & also fit the upper corroded area. The drive-shaft size is 1/2" & the outer diameter of the seal is 1 .125". Once this stub shaft is made & lubricated with Vaselene to keep the J-B Weld from adhering, mix the epoxy, pushing it into place & wait for the curing to take place. Once cured, the bond to the stub shaft (if there is any) can be broken loose by rotating the stub shaft. If you are replacing the upper shaft seals, you will have to be sure that this new epoxy area is slightly larger than the seal OD as you do not want to break the epoxy that you just put in. The corrosion will not usually be low enough into the housing to effect the outer seal surface. When cured, file the epoxy flat with the top of the housing.

The photos below show the stub shaft on the left. On the right photo, the built up epoxy is marked in purple & identified by the arrow A. Arrow B shows the shifting rod seal bushing in place. Note, that there needs to be an opening at the rear into the rectangular hole coming from the water intake. Do not mistake material being gone here as being corroded out. If you build it up here also you have effectively blocked all water into the water pump.

Water Pump: If the pump housing is the older pot metal as used on the very early motors, replace the whole pump unit with the newer nylon housing kit which has a stainless steel liner that fits inside the housing. There is also a stainless bottom plate, this plate has to be positioned with the suction hole in the proper location/relationship as indicated in the photos. If you are just replacing the impeller, you can tell which way is up by observing the wear of the impeller on this plate. The impeller fits in this stainless cup liner which gives a very long lasting situation. In most cases you will never need to replace the water pump assembly, just the impeller. Sometimes the rubber impeller becomes un-bonded to the metal hub.

Things to look for after the water pump is removed are, the impeller can take on a curl rather than have the blades snap straight outwards when removed from the housing. It may have also picked up some sand or some other type abrasive material which has created a scoring in the lower impeller plate and/or upper housing. That scoring alone would have a tendency to create a air pocket creating inefficiency in the pump.

On these motors, the water goes to the outer water jacket first, the overboard water indicator line comes off the lower jacket (closest to the pump location). This overboard water indicator will have water first, before going into the rest of the motor. Therefore if you do not have water coming out of this indicator hole, & YOU ARE SURE THAT THERE ARE NO BLOCKAGES, your water pump IS NOT WORKING.

One rule of thumb is: if the engine overheats and the water pump impeller doesn't look like it just came out of the box, replace it --- then should the problem still persist, go further into the system as needed. Of course be sure the outlet tube & grommet is fitting correctly. But you have eliminated the most likely source of the problem to start with.

The driveshaft may have a O-Ring around it on the splines that engage the motor crankshaft. The earlier motors had a groove around the shaft for this O-Ring, while the newer ones had the O-Ring in a internal groove in the lower end of the driveshaft. If it on the shaft, remove it until you are ready to re-install the parts. If it is the newer type with the O-ring internally in the bottom splines of the crankshaft, you will not see it unless you pull the powerhead. Don't worry about it if your shaft does not have a groove in the upper splines.

Now on the gear case unit, you will find 4 bolts holding the water pump with the driveshaft going thru this pump housing. The housing can be of pot metal or plastic, depending on the vintage. The plastic/nylon type is the newer style. If it is the pot metal type & has been using saltwater, you may consider replacing the whole pump with the plastic style instead of just the impeller, as the internal portion where the impeller rubs will be corroded & will soon chew up a new impeller .

Unscrew these 4 bolts & slide the water pump housing up & off the driveshaft. The front 2 screws are longer than the rear ones for the original units. Keep this in mind when you reassemble the unit. If you purchase a new water pump kit it includes the impeller, seals, O rings & a new housing with 2 shorter screws as the new housing is slightly different. Make note of which direction the impeller vanes are facing, as you need to install the new impeller the same way, otherwise it will not pump right. Now also there will be a key that holds the impeller to the shaft. Save this also for reassembly.

If you take it apart & the impeller appears still intact, you should consider inspecting it further, as it is not uncommon for the inner hub to become unbonded from the rubber impeller, allowing the hub to spin inside the impeller rubber. Also some aftermarket impellers can be thinner than the originals, not sealing on the sides, sucking air & creating erratic pumping.

It is recommended you replace the water pump to outlet tube grommet. This grommet has been improved in that by looking at the illustration below, the sides now have been made wider & taller. This appears to be to elevate the problem of upon final assembly as you are trying to align this tube into the grommet & slide the lower unit upwards trying to align the driveshaft splines into the crankshaft, (all without much vision). Many times the grommet has been known to not slide over the tube properly, therefore giving a chance to allow the outlet water from the water pump to leak somewhat. This can be checked by running the motor with muffs over the water intake, & watching at the upper part of the lower unit where the shifting rod goes up to the powerhead. If water is being forced out around the shifting rod grommet, you can bet that the water pump grommet is not seated correctly. This new grommet is designed to help eliminate this problem, so it is recommended that you replace it when replacing an impeller.

There is also a large neoprene O-Ring that is slid over the top of the water pump housing. This helps align the lower unit & water pump into the mid section housing. You if you have the older units you will also see 2 different length bolts that attach the water pump to the lower unit. The longer ones go forward as the pump is thicker there. The newer units utilize a slightly different impeller housing & use the same length bolts.

If you have been having water problems, you may consider at this time, fabricating a garden hose adapter to the copper water supply tube leading to the powerhead. This is made from a 5/16" or 3/8" ID rubber or vinyl tube attached to a 3/8" barbed fitting that is then screwed into pipe bushings & then into a garden hose to pipe end. You can hose clamp the rubber/vinyl tube onto the barbed fitting. Then with the lower unit off the exhaust housing, hose clamp the loose end onto the motor's 3/8" copper tube.

Without the motor running, turn on the garden hose water supply, starting slowly until you see what is happening. If nothing, or very little water exits the overboard tell tale hole, poke the small wire up there to clean it out again. On the early 1974 motors that did not have a overboard tell tale hole, this method will not work. Turn the water on full force & see if you can force debris, salt or sand out using this method. If there is a blockage somewhere, you will not get any (or very little) out the rear blubber hole if it is a pre 1977 or the pee hole if later.

If you have some flow out the pee hole, but there is considerable debris, you may have to constantly poke the wire into the pee hole to clear this exit hole. I have also made a 3/16" wire into a crank handle type thing & flattened the upper end. You can poke it up the motor supply tube & rotate it to see if any debris is in this tube. If this does not do it & if it is apparent that there may be considerable debris inside, or a blockage somewhere, then you should probably remove the head itself as on these motors prior to 1987 it is easier than just the thermostat cover. Now remove the thermostat cover & you can see if there is a blockage or bad thermostat.

One thing about using this method is that you can isolate if it is the water pump, or a blockage inside the powerhead or water jacket passages.

Reassembly of Water Pump: Place the new impeller in the water pump housing with the vanes ALL pointing in the same direction as when you took the old one out. If you forgot, remember that the motor rotates in a clockwise direction, therefore the vanes need to be pointing in the opposite direction as the motor is rotating as the rotating shaft will force the vanes back. Also take into consideration that you maybe assembling this unit upside down before you slide it onto the driveshaft. If you get them in wrong, it probably will not hurt, as when the motor is started, the centrifugal force of the rotation more than likely establish them in the right relationship anyway.

It is a good idea to put a slight amount of oil on the impeller vanes at this time also. The new plastic housing pumps have a stainless steel inset that the impeller rotates inside of. This insert has to also be aligned & in the right place when assembling the upper housing. You will have to slightly force the impeller to one side as the housing is not centered but is eccentric with the shaft to make the impeller pump water. With the impeller in the stainless cage, slide the pump housing & impeller unit onto the shaft, Again be SURE that ALL the vanes are pointing in the same direction. Remember the rotation of the engine is Clock-Wise.

I have found it best to install the upper pump housing on the shaft with the shaft while NOT in the lower unit. The shaft simply slides into the splines in the lower gear. The shaft can be put back in more easily after the impeller & upper housing are installed, than trying to fight the impeller & key position with no room to work against the lower impeller housing.

Slide the water pump unit with impeller installed, down to near the flat on the shaft for the key, then place the key in the shaft’s flat, (chassis grease may help hold it). The driveshaft has a flat in this location, but the key may be just a round pin. Now move the pump housing down & rotate it to a location that the notch in the impeller & the flat on the driveshaft make it easy to install the key. If you insist on a better key, a Mercury impeller key can be shortened to fit. The Mercury keys are made in the form of a brimmed hat of extruded stainless. They fit the flat better & have the rounded key made as an integral part. These Mercury keys are usually are too long & need to be shortened slightly.

Align the drive shaft so the key is even with the bottom of the impeller. Now you can slide the shaft & upper housing/impeller down into the lower unit, engage the splines in the gear & install the four bolts on the top of the housing. Once the pump housing is down & in place you can now replace the 4 bolts holding the housing to the lower unit. Remember the pump housings require 2 longer bolts in the forward part as compared to the shorter 2 rear bolts.

Be sure that the rubber grommet on the rear of the pump housing is in place with the 2 rubber ears in the corresponding side holes of the housing. These ears hold the grommet in place when you slide the copper tube into the grommet on final assembly.

You might consider placing a smear of Vaseline or chassis grease on the lower end (where it mates into the grommet of the pump housing) of the copper tubing water tube leading up into the exhaust housing. This grease helps insure this grommet does not get pushed out of position.

There is a large rubber O-Ring about 1 1/2" in diameter that sits on top of the water pump & between the exhaust housing, this ring more than likely will stay in the housing., however it may come off & be still on the upper pump housing. It is essentially a seal & alignment between the water pump & the exhaust housing. Check to see that it is still in place. You might want to clean it up & apply a light coat of grease on it to ensure that it also aligns readily.

Replace the rubber smaller O-Ring (5/8" OD x 3/32"width) on the driveshaft, & grease the splines with a marine wheel bearing grease. This O-Ring goes in a groove around the upper splines about 7/8" down from the upper end on motors up until at least 1983. Somewhere in the mix the later motors used a internal circular groove in the female spline of the crankshaft. The purpose of these O-Rings is to retain the grease in & around the splined shaft & to also keep water out, trying to eliminate the driveshaft from being stuck in the crankshaft extension. If you forget to grease these splines, the next person to tear this motor apart 10 years from now may have trouble getting the shaft to separate from the motor.

If your motor is from about 1976 on, then replace or check to see it is still in place, the stainless steel baffle screen that is slid into (supposed to be staked in) the rear divided section of the exhaust housing at the juncture where the gear case fits together. It simply slides in a slot & is held in place when the exhaust housing & gear case unit are assembled. If this is left out it may increase the noise level to some degree.

For a short shaft motor, you have to align the copper tube, the driveshaft splines with the crankshaft & the shift linkage rod at about the same time. Slide the complete gear case up to where the linkage rod is in the clamp. You can look in & see if the shaft groove is in the proper location.

For a long shaft motor, there is an extra rubber bushing about 4" long that goes into a cavity of the extension. This has a hole in the middle that the water tube goes inside of & is automatically aligned with the water pump outlet. HOWEVER, if someone has made the 3/8" water pump tube extension by just expanding 1/2" of one end, you will need to make a spacer (1/2" tubing about 3/4"long) to slide over it so that this tube bottoms out inside the above mentioned 4" rubber bushing. You will need to do some measuring to insure that this extension tube will be secured inside the rubber bushing about 5/8" (or the same amount needed to match what is needed to fit inside the the water pump grommet) above the lower edge of the housing extension.

This is needed otherwise when installing onto the exhaust housing, which you can not see what is happening, this extension tube may well be pushed all the way into the water pump outlet grommet, bottoming out against the lower water pump plate & totally blocking any water from being forced up into the water tube.

Be sure you completely remove upper clamp screw from the coupler clamp. You need to be able to see thru the screw hole & tell whether this location is in line with the groove in the upper shifting rod so you can put the screw back in place with minimal difficulty. If the upper shift rod is not down far enough, shift the shifting lever into forward, this will force the linkage down slightly. Now pull the lower shifting rod that is in the lower unit up putting the gearbox into reverse. This gains you enough to get the bolt in the clamp.

Place the upper clamp bolt in the clamp (it may help to use a spring fingered type pickup tool to hold it in the narrow slot between the units) & tighten the screw. With everything now in place on the exhaust housing, push the lower unit up, being sure the copper tube is still aligned & in the rubber grommet of the pump housing. At this same time you need to have the driveshaft splines engage the motor’s crankshaft splines. If it does not go readily, you may have to either rotate the flywheel or the prop, or both. As everything slides together the shifting linkage will move the lower rod down to match the forward position of the shifting lever. Once everything slides together, you can replace the 6 bolts holding the lower unit to the exhaust housing.

If you get it all back together & running, but you still get no water spraying out the overboard water indicator hole, quickly get your small wire & again poke it into the hole to try to break up any debris that may be lodged in the small overboard hole.

OK, Your Reassembled it & Now it Doesn't Pump Water: This one can be a head scratcher. Is the pee hole line plugged, however the block was getting hot? Did I misplace the impeller key. Did I forget the water pump lower impeller plate? Did I get the water outlet line in the grommet wrong? Is the water pump housing tightened down? Is my test tank loaded with debris & are the intake screens plugged? ???

All I can say is tear it apart again, (it now takes me 40 min to tear down & reassemble). The one thing I double checked was the impeller inner hub may have become separated from the rubber impeller. No, that was fine. A new impeller sells for about $15.00.

I had the above happen in a 1987, described above, that after a complete rebuild, & using the new impeller, it would run for 1 minute squirting water out the pee hole before the flow diminished & then steam started coming out. I shut it down for a few minutes & started over, exactly a repeat of before, & again for the 3rd & 4th times. Took the thermostat out & some water comes out while running, but not as much as expected. I tore it down the second time & still found nothing that I was sure was the problem.

After reassembly & test running, the same problem existed as before, so another tear down was on the horizon.

This time however I found another used water pump housing that did not look much different than the one that was on the motor. I steel wooled the stainless liner shiny, & replaced the then as new impeller. But before I installed the lower unit, I fabricated the above shown water-jacket flush adapter & attached the plastic tube to the water supply tube to the motor & flushed it with a full force of the garden hose. Water came out with force in every place that I would have expected it to.

Upon another re-assembly & placing the motor in the test tank this time it ran like it was supposed to. I'm not really sure what I did, but maybe there was some sort of a blockage that floated around inside the block & at times would block the flow & the water pump was not powerful enough to dislodge it, OR the 3rd time maybe was a charm. I am not complaining enough to investigate any further however.

Removal & Replacement of the Shaft Seals Without Disassembling the Lower Unit: To remove the prop shaft seals without tearing the whole lower unit apart, you can make or purchase a slide hammer puller that has a metal screw on the front end. These can usually be purchased from automotive repair shops or Harbor Freight. Screw the screw into the seal being careful to not gouge the housing or the shaft. Tap the slide hammer handle a few times & the seal will usually start to move. Once it is out, go back & do the same thing again on the inner seal. These two seals are identical, but are placed back to back. This is to ensure that one seal seals the water out & the other seals the oil in.

Replace them the same way they came off. You will need some sort of a solid round object to drive the seals back in with. Sometimes you can find a 1/2" drive deep socket that may be of the appropriate size to put pressure on the outer rim of the seal.

Disassemble or Rebuild the Gearcase: The lower unit, or gearcase needs to be taken off as if you were replacing the water pump impeller.

Remove the (2), 1/4" screws that come in from the rear above & below the propshaft exhaust opening. You may luck out & be able to rotate the bearing housing & pull it rearward & then tap or pry it back. However be careful not to break anything, so look at the next paragraph.

OMC makes a gearcase bearing housing puller #386631. The puller pictured below is a actual copy that I made off the original OMC puller drawings. You can make your own simpler puller by using (2), 5" pieces of 1/4" X 20 TPI, or course all-thread, (6) 1/4" nuts & (2) flat washers for the stand offs. The puller cross bar needs to be 1/2" x 1 1/2" flat bar 5" long. In this cross bar drill (1) 1/2" hole in the center. Then on each side of the 1/2" hole drill (1) 1/4" hole 1 5/8", so that these 1/4" holes are 3 1/4" apart with the 1/2" hole in the center of them. Now screw (2) nuts onto the rod & at about the middle & lock them down, one against the other. These double nuts now give you something to use to screw the rods into the gearcase with. Screw the other nuts, (1) on each rod in from the outermost end in about 1", and slide the flat washer on outside of the nut as added support when you assemble everything & start your pulling.

In use, these rods are threaded into the existing 2 holes which the bearing housing is retained to the gearcase with, & act as a guide & stand-off when pulling. Thread these rods into the existing holes so & adjust the 2 end nuts are about equal distance to accommodate any length needed to set the crossbar in the appropriate position.. The crossbar slides over the rods on the outer ends of the rods. The propshaft goes thru the crossbar's center 1/2" hole. The prop nut is now reinstalled onto the shaft outside of the crossbar & it is used in conjunction with the other puller rods to pull the shaft, which in turn pulls the bearing housing out of the gearcase. You may have to hold the propshaft with pliers to keep it from turning, being careful to not mar the splines when you tighten the prop nut to pull this unit.

The bearing housing only has to move about 3/8" to come free. It comes hard enough that you WILL PROBABLY need this puller to do the job. It will usually come hard for the first 1/8" or so, as there will usually be some debris around the inside of the housing around the large internal O-Ring that acts as a sealer between the bearing housing & the gearcase.

If the bearing housing is frozen into the gearcase, it will usually be at the rear as the housing slides into the gearcase about 1/2". If the motor was used in saltwater & not flushed good, there may be salt corrosion between the 2 parts enough to seize them together. If this is the situation you may be able to see where the gearcase has cracked in this area because of the corrosion. There is a lot of internal pressure here from the corroding salty aluminum. You can try penetrating oil, tapping the areas with a hammer, even trying some heat from a torch, but in my experience you are wasting your time. If you do get it apart, the damage is not really reparable. If so, many times you will not be able to pull the bearing housing out without ruining things. If this is the case, it is suggested that you leave it alone, refill the gear oil, replace the drain pug seals & run it as is until you can purchase another better used gearcase assembly, & then try to salvage yours out for spare parts. I have seen one so bad that the only way to get it apart was to cut it in numerous sections with a metal bandsaw. It was so bad that no internal parts were salvageable.

Unscrew the shift rod that is protruding upward in the front section of this unit. It will unscrew about 3/8" & then can be pulled upward & separated from the unit. You now have to remove the #2 Philips headed screw from the RH outside of the lower case. This is the pivot point for the internal shift linkage.

Disassemble & Inspect the Internal Gearcase Parts: Now you can disassemble all the internal parts, clean & wash them off in solvent & inspect for any damage. There are (2), 7/32" steel balls with a spring between them that go thru the propshaft that keeps the shifter (clutch dog) in place. One thing to observe when taking the parts out is the condition of the old gear oil. Check to see if it has any filings or metal flakes, gear teeth, which would be indicative of bad bearings or gear parts. Lay the parts out in a sequence that you took them apart. Your service or parts manual becomes invaluable here. You may even want to use a digital camera to record where things came from.

Check the shifter (clutch dogs) to see if they are battered on one end. There are 3 of these dogs on each side, which engage either the forward or reverse gear. If the forward side leading edge has become battered slightly, (probably because of improper linkage adjustment) the shifter can be reversed on reassembly so that these battered dogs now engage on the reverse side. This should have minimal problems as reverse is used way less than forward to neutral.

If there has been a water leakage into the gearcase & or it has sat unattended over a winter season or more, the bearings could be rusted & need replacing. There are (3) Torrington needle bearings, (1) small thrust ball bearing & (1) Timken tapered bearing in this unit. There are also (1), O-Ring seal around the shifting linkage, & (2) sets of double seals placed back to back on the driveshaft & also (2) on the propshaft. These seals are priced at about $14.50 each & the O-ring at $1.00. It may be advisable to replace them while you have the unit apart if there is any doubt of leakage, either in our out.

Exploded View of the lower Unit

The below part numbers & nomenclature was taken from a 1978 parts list which should be the same for all 1974 thru 1992
it is possible that some of these numbers could currently be superseded

	388001	GEARCASE ASSY, Less driveshaft & pump	35	319085	SEAL, Impeller housing
1	388276	BEARING HOUSING	36	301551	WASHER, Connector to shift rod
2	321481	SEAL, Bearing housing to prop shaft	37	302497	GROMMET, water tube lower
3	386125	BEARING, Reverse gear	38	388289	IMPELLER HOUSING & SEAL ASSY.
4	386231	BEARING	*39	318972	SEAL, Impeller housing to driveshaft
5	318877	CRADLE, Clutch dog	*40	386084	IMPELLER ASSEMBLY
6	304071	SCREW, Bearing housing to gearcase	*41	300611	PIN, Impeller to driveshaft
7	308627	"O" RING, Bearing housing to gearcase	*42	318995	PLATE, Impeller housing
8	318861	GEAR, Reverse	43	321455	DRIVESHAFT, Standard
9	322097	PROPELLER SHAFT	44	552906	COTTER PIN, Prop nut to shaft
10	316505	SPRING, Detent	45	318971	NUT, Prop
11	316506	BALL, Detent	46	318959	THRUST WASHER, Prop shaft, rear
12	316501	SHIFTER, Clutch dog	47	318992	SHIFT ROD, Lower, standard length
13	388416	SHIFTER LEVER & YOKE ASSY.	48	304024	SCREW, Shift rod connector
14	308376	PIVOT PIN, Shifter lever	49	303794	CONNECTOR, Shift rod
15	386076	GEAR & BUSHING ASSY, Forward	*50	322087	CUP, Impeller housing
16	386186	ROLLER BEARING, Forward gear	51	386670	PROPELLER, 9 x 10"
17	322341	PINION, Driveshaft	51	387389	PROPELLER, 9 1/4 x 8"
18	322202	THRUST WASHER, Lower pinion gear	51	386118	PROPELLER, 9 1/2" x 10", Standard
19	388000	THRUST BEARING, Pinion	51	386669	PROPELLER, 10" x 5"
20	322201	THRUST WASHER, Upper pinion bearing	52	319484	CONVERGING RING
21	388002	GEARCASE, Bearing & seal assy	53	386119	PROPELLER BUSHING ASSY
22	388014	BEARING ASSY, Driveshaft	54	303067	"O" RING. Driveshaft
23	318874	SLEEVE, Bearing driveshaft	55	308744	SCREW, Gearcase to exhaust housing
24	321480	SEAL, Gearcase to driveshaft	Below are parts for the 5" longer or "Long Shaft" versions
25	301877	"O" RING. Bushing to shift rod	43	321456	DRIVESHAFT, Long shaft
26	304765	BUSHING, Shift rod	47	319298	SHIFT ROD, Lower, long shaft
27	321738	WASHER, Seal shift rod	54	303067	"O" RING. Driveshaft to crankshaft
28	386071	BEARING ASSY, Pinion to gearcase	56	308744	SCREW, Extension
29	318991	SCREEN, Water intake	57	319340	EXTENSION, Impeller housing to exhaust housing
30	307551	PLUG & WASHER	58	320025	TUBE, Water
31	311598	WASHER	59	202893	"O" RING. Water tube extension
32	318966	THRUST BUSHING, prop	60	319314	EXTENSION, Gearcase "Long Shaft"
*33	324334	SCREW, Impeller housing to gearcase, short	60	123023	EXTENSION, Gearcase "Extra Long Shaft"
*34	324474	SCREW, Impeller housing to gearcase, long	61	389112	WATER PUMP REPAIR KIT
* Contents of water pump repair kit			62	389114	CHROME PUMP KIT

Removal & Replacement of the Shaft Seals When the Unit is Apart: To remove the prop shaft seals, you can make a puller by using a 5/16" or 3/8" rod about 15" long. Make a sharp bend on one end, that protrudes out about 3/8". Grind both top & bottom of this protrusion so that there is a flat on the bottom & no radius on the inside. Thread the other end long enough to accept a couple of nuts. To remove the propshaft seals, screw a couple of nuts on the end, jam them tight so that no part of the threaded rod protrudes. Lay the bearing (propshaft) housing on a flat surface with the rear surface down. Insert your removal rod down inside the bearings & against the rear seals. Pound down on the nuts with a hammer, removing the seals from this housing. Another method would be to drive them out from behind using a 9/16 in long socket and a hammer with the bearing housing sitting vertically, outer side facing down. Place the socket through the back and through the larger inner bearing. Then hitting the smaller outer bearing, drive the bearing and the 2 seals out.

You will notice that 2 these seals are installed back to back, this is a dual purpose, one is to seal the oil from escaping from the inside & the other is to seal the water out. Replace them the same way they came off. You will need some sort of a solid round object to drive the seals back in with. Sometimes you can find a 1/2" drive socket that may be of the appropriate size to put pressure on the outer rim of the seal.

For the driveshaft seals, you can use the same removal rod as above, but inserting it from the top & hooking the protrusion under the seals. Install the slide hammer & again the nuts on the end. With the slide hammer, pull these seals from the upper gearcase unit. These might well be in rather solid, & you may have to resort to a Dremel tool & a cutter to remove some metal from the seals to relieve tension. DO NOT cut so deep that you nick the gearcase, as this would allow water/oil leakage. It seems to work best to tip the gearcase upside down in this instance while you are pounding downward. Once they are out & things are cleaned up, replace the seals the same back to back installation as described above. It should noted that care need to be taken to keep any residue out of the bearings. This can be done to some extent by tamping a section of paper towel into the bearings, and removing it just prior to reassembly.

If you need to replace the needle bearings in either of the above units, do so before you replace the seals. You will need a puller about the same as the one mentioned above to pull the bearings. And properly sized bearing cup bushings are needed to drive the bearings back into the housings

The lower shifting rod can become pitted at the O-Ring seal area. If this is the case, either replace it, or since it is stainless steel, you can silver solder up the pitting & then lathe turn or bandsand & back down to close to the original size & polish it. Is does no good to rebuild this unit & then allow a minor spot to be a leakage point. To replace the O-Ring seal for this rod IF you are to totally disassemble the unit, you will need a slide hammer type puller. Take a 1/4" All-Thread about 15" long, slightly taper one end, & grind off the corners of a 1/4" nut so that it will just go inside the hole (about .400" diameter) in the lower unit that this shifting rod goes into. Push the pointed end of All-Thread down thru the shifting rod hole in the gearcase housing. Using a flexible spring loaded pick-up tools, position the ground off nut inside the gearcase housing & thread the All-Thread into this nut. Make a bar of steel with a hole drilled in the middle or you can use a steering wheel puller laying it across the top as shown below in the right. Just tighten the top nut, pulling the to pull the seal & bronze guide as a unit.

Clean them up, & in all probability the lower steel washer used under the O-Ring seal on the older units may get deformed in this pulling operation. Hammer it flat again. The newer units use a nylon washer. With this nylon washer, you may well ruin it by pulling the nut into it during the removal process.

Remove the old O-Ring from inside the brass guide, clean up the O-Ring recess, install the new one in the brass guide. This O-Ring is a normal O-Ring that you may find in any well stocked plumbing supply store & has a 1/4" hole, 5/32" thick & 9/16" outside diameter. Place the washer in the hole first & be sure it goes to the bottom of the hole & is setting there flat, (not tipped). Now with a fingered pickup tool place brass guide & O-Ring assembly down & started in the hole in the lower unit that they came from.

Use a 1/2" rod to drive all these parts back down into the gearcase housing until they bottom out in the pocket.

Another important thing to inspect is the water intake screen that is in this unit. If the screens have been damaged, which can be observed from the outside, it should also be replaced, as if large intake holes are there, then debris can get sucked into the water pump & farther up into & possibly plug the internal water passages. This is simply a small plastic basket that is tapered on 4 sides & has perforation holes on 2 sides which acts as a filter for larger debris. The screen is inserted into a blind hole of the intake cavity. The old screen is removed by simply using a long screwdriver to break it apart enough to remove the pieces. The new one is inserted by making a wooden insertion tool the shape of the internal part of it & tapping it down into place.

Reassemble the Internal Gearcase Parts: Once everything is ready, now you can start reassembling. Put the Timken tapered bearing in it's race in the front of the housing first. The manual calls for the use of a shifter yoke locator tool. This is nothing more than a speedometer type cable or soft wire about 20" long, with a short 10-24 size screw (same size threads as the shifter rod) silver soldered to to one end. Some mechanics say you can get by without it, but experience indicates it's usage far outweighs the problems encountered without it. In use the cable is fed down thru the shifter rod bushing & O-Ring unit, out the bottom & rear of the gearcase enough to allow it to be screwed into the shifter yoke maybe 2 threads or so. The forward bevel gear is positioned in place on the shifter yoke. The clutch dog cradle should be snapped into place on the yoke arms & then these parts guided in this unit in from the rear & being guided by pulling on the cable, you can guide it into place. This is a tight fit to get things down low enough, yet keep the lower shifter yoke aligned to go into the lower slot & at the same time pull the front end with the locator tool.

Now you can install the pinion gear. But to get in in place you need to slightly tip the forward gear down in front to allow enough clearance to get the pinion gear to be installed. The upper thrust washer, thrust bearing (not a real bearing, but a hardened washer like bearing), & lower thrust washer. These 2 thrust washers are a different thickness. Place the thinner on onto the pinion gear first with the outer chamfer down, then the bearing & lastly he upper, thicker washer goes on it with the chamfer edge up. You now need a approximate 5/16" dia. rod with a 1 1/2" 90 degree bend on one end, forming an Ell. A 5/16" long shank Allen wrench will work. On this assembly rod tool, you stack the pinion gear, bearing & washer unit, which you can now guide into the gearcase housing & up into the lower driveshaft bearing.

Once everything is in place, you can now look thru the pivot hole in the outer RH side of the housing, by pulling the locator tool & using a long screwdriver, jockey the gear/yoke until the yoke hole aligns with the housing hole. You might have to use a long pointed ice pick type tool to really align it once you get it close. Then install the Philips headed pivot screw which you have installed a new seal under the head, into the gearcase & into the pivot hole of the yoke.

Next you will have to reinstall the lower shifter rod down thru the O-Ring seal & align it with the threaded end of the shifter yoke. You might need the use of a flashlight & slightly moving the yoke internally to get the yoke's threaded end to be in line to allow the shifter rod to be threaded into it. Screw it in until it stops, & if the bend is not facing forward, back it up to where the bend does face forward.

Now, with the use of a spring fingered type mechanics pickup tool, you can position the clutch dog (which as a groove on each dog that goes forward) on the cradle & push it down, then rotate in into place with these 2 grooves pointing forward.

Take the prop shaft, install the detent spring & apply some trailer wheel bearing grease on the outer ends of the spring & at the holes in the shaft. Position the 2 ball detent ball bearings in this grease to hold them in place temporarily. Slide the propshaft down into the gearcase taking care to align the ball bearings with the ears of the clutch dog, which has a slight taper at this location to allow the springs to be compressed & slide inside the dog. Push the prop shaft in thru the forward gear & into the front bearing. If the shaft does not want to go far enough down, then with the shifting rod, pull it out sliding the shifter dog rearward & allowing the ball to slide inside the dog.

Now the reverse gear can be slid onto the propshaft. Be sure the rear bearing housing has been cleaned on the forward end & a new O-Ring installed. Lightly oil the O-Ring & the propshaft. This rear bearing housing can now be slid on the propshaft & aligned with the 2 rear holes & tightened up. It may be advisable to place some anti-seize on the inner rear mating surfaces & the threads before reinstalling them so that disassembly is assured the next time someone tries to take it apart.

The driveshaft & water pump can now be installed on the gearcase housing & the whole unit then reinstalled on the motor's exhaust housing as described before in the water pump replacement section.

Pressure Test the Gearcase: If you are not rebuilding the gearcase, but suspect a leak, drain the unit, install either the drain/fill or the oil level screw, then apply 7 to 12# of air pressure with a Mity Mite, to the other remaining open oil screw hole. That should allow you to find the actual source of the leakage either by sight, sound, or both if using soapy water so you can see the air bubbles if it is leaking.

At that point, once you have identified the leak, it's a matter of replacing that seal, and whatever might be related to it if that related item should also be faulty.

Another bit of advise, even if you have rebuilt the whole lower unit & replaced all the seals, it is a good idea of doing the pressure test BEFORE you fill the gearbox with oil. You may have nicked the shifting rod O-Ring or had the bottom washer fall out of the hole just before you put the brass guide & O-Ring down in place, & are having a leak there. If you refill the oil & have this seal faulty, gear oil will run out the hole discussed above that needs to be cleaned to allow water to drain out.

I had the above happen to me once & I really did not want to tear the whole gearbox apart AGAIN. What I did was pull the lower unit off as if I was replacing the impeller. Now I could see down inside & verified the oil was seeping out of the shift shaft O-Ring area. I drained the gear oil & saved it. I unscrewed the shifting rod. Next I used a 5/16" X 18 tap & tapped the brass O-Ring guide. Before starting I smeared boat trailer bearing grease on the starting flutes of the tap to catch the chips & keep them out of the gearbox. I used a 1/4" square socket to attach to the tap & a speed handle to do the tapping. After removing the tap, & welded a 5/16" bolt onto the 1/4" all-thread I had used for the earlier mentioned puller & with the slide handle, easily pulled the brass guide out of the housing.

After replacing everything, the shifting rod had no problem aligning into the shifting yoke threads deep in the unit as the thread ends have a slight tapered point that allows it to easily start into the threads.

Replace the Gear Oil: There are 2 types of gear oil available, (1) the old regular type oil & (2) the newer synthetic oil. These motors have ran for years on the older type, but the new synthetic oils are a lot slipperier, giving a lot better lubrication. The synthetic oils will a little higher priced, but you get what you pay for & the synthetics give a cooler running & longer life for your motor. The one way to tell the difference between the two if you are trying to refill a unit that is unknown as to what type of oil is in it, is that the regular oil is usually a honey colored while the synthetic is a greenish blue. This will not hold true IF the oil has been there for some time & has turned black from usage.

In replacing this gear oil, it is a lot easier to use a special pump & adapter that is made for this operation & many times comes as a unit when you purchase the bottle of oil. It is a push handle made into the cap of the oil bottle & operates a small pump in the bottle with a hose & threaded nozzle that screws into the drain hole of the lower gearcase unit. In operation, you remove the upper screwdriver slotted large plug (this is the vent & oil level plug). Now remove the lower plug that is the same size as the upper, (DO NOT REMOVE THE PHILIPS HEADED SCREW LOCATED NEXT TO IT) The Philips headed screw is a pivot screw for the internal shifting linkage. If you remove it, things can get hairy trying to align it back into the shifting yoke, as this is normally done while the gearbox is apart & you can see when you are positioning it.

Screw the proper threaded hose fitting into the bottom hole & pump the oil in until it starts to run out the top. Replace the top plug. In replacing this plug first, you are now creating just enough of a vacuum on the oil that will allow you to unscrew the oil hose & install this lower plug before a lot of oil runs out.

Reinstall the Gearcase onto Midsection: Before you go too far, 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. This can make for easier disassembly later on to insure that the bolts to not get seized up in the motor parts that are underwater.

For a short shaft motor, you have to align the copper tube, the driveshaft splines with the crankshaft & the shift linkage rod at about the same time. For a long shaft motor, there is an extra rubber bushing about 4" long that goes into a cavity of the extension. This has a hole in the middle that the water tube goes inside of & is automatically aligned with the water pump outlet.

Place the shift coupler on the lower shifting rod protruding from the gearcase, align the groove with the holes in the coupler & tighten it in place.

Slide the complete gear case up to where the upper linkage rod from the powerhead is in the clamp. Be sure you completely remove upper clamp screw from the coupler clamp. You can look in & see if the shaft groove is in the proper location of the upper hole as shown in the illustration below. You need to be able to see thru the screw hole & tell whether this location is in line with the groove in the upper shifting rod so you can put the screw back in place with minimal difficulty.

If the upper shift rod is not down far enough, shift the shifting lever into forward, this will force the linkage down slightly. Now pull the lower shifting rod that is in the lower unit up putting the gearbox into reverse. This gains you enough to get the bolt in the clamp.

It is possible to tighten this coupler with either of the thru bolts NOT in the retainer groove. If this happens, you may not be able get it in gear, or if it does it will not come out into neutral. Plus you have probably stripped the bolt threads. A new bolt is a stainless steel 1/4"-28 TPI X 1/2" long. You can cut your own screwdriver slot by hacksawing it in or using a Dremel tool cut-off stone.

As you slide the gearcase up to mate with the midsection you need to have the driveshaft splines engage the motor’s crankshaft splines. If it does not go readily, you may have to either rotate the flywheel or the prop, or both.

Once everything slides together, you can replace the 6 bolts holding the lower unit to the exhaust housing.

Lower Thrust Mounts Worn: Here there are 3 squarish rubber mounts, one on each side that are called lateral mounts & a front one that is the actual thrust mount. The side mounts do not normally wear, but the center front one is the one that takes the pressure. This one can get crushed & when it does it will allow you to get movement by pushing/pulling the lower unit forward or backwards. The side mounts can be replaced by removing the 2 cross bolts in the mount brackets.

Replacing the front mount is possible without dropping the lower unit IF you make a tapered wedge out of wood, & drive it between the pivot housing & the midsection. The problem here is that the shifting rod goes thru the pivot housing & there is really not enough room to tweek it without help of the wedge. With the 2 units held apart by the wedge, you may now be able to by using a large screwdriver to force the front thrust mount out of position. The new one goes in a lot easier than the old one came out.

It is possible to place a rubber shim between the actual worn mount & the center post that it bears against as a temporary fix. One that I found was crushed to the point where about 3/16" shim was required.

Shown here by the blue arrow is the front thrust mount, with the lateral rubber one in the center of the photo. These rubber mounts have (2) 1/4" holes running forward & aft apparently to conform somewhat to the round housing it bears against in the front. After time the rubber may loose it's elasticity & you may get about 1/8" to 3/16" excess movement here.

The (2) 1/4" holes above & below the actual arrow point are for the cross-bolts that retain the brackets.

Here salt corrosion built up inside the front housing which popped holes in the housing.	Salt corrosion with a mix of unburned exhaust oil because of a plugged drain hole.

A lathe turned stub shaft as described above	Water pump base rebuilt with J-B Weld shown in purple

Improvised seal puller	Pulling the shifting rod seal with a puller

Lower thrust mount shown	A worn thrust mount on the left, with a new one on right