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Gear End Yoke Seal Replacement

This page is for Pre-Alpha, Alpha One and Generation II drives. The replacement procedure is basically the same for Bravo but the parts will be different.

Outdrive oil sometimes will get inside of the boat because the seal on the gear end yoke in the upper housing of the outdrive is not sealing. ( Item # 20 )
If this problem is not corrected, you will be low on outdrive oil and will burn up the upper gears and bearings.

To replace this seal on a Pre-Alpha, Alpha One and Generation II drive, you must place the shift lever in forward gear on standard rotation drives and remove the outdrive. ( On a counter rotation drive, it must be placed in reverse ).

Once the drive has been removed, you must now unscrew the 3 7/8 retainer nut in the upper housing of the outdrive with a retainer nut wrench.

After the 3 7/8 nut has been loosened ( counter-clock-wise ), it may be necessary to use a block of wood to pry out the engine driveline assembly. As you pull this assembly out, be sure to watch for a number of 3 7/8 diameter shims. Some of them may stick to the back of the drive gear bearing which is coming out and some may stick inside of the housing. DON'T loose any of the shims. Take all of the shims ( .080 to .090 ) and wire tie them together for reassembly.

Clamp the retainer nut wrench in a vise and place the driveline assembly in it upright. Before going any further, turn the 2 large bearings by hand to see approximately how much force is required to make them turn. Remember this for reassembly.
Now use a Dremal with a cut off wheel and put 2 small reference marks (1) on the end of the gear end yoke and (1) on the locknut which holds everything in place. Once the 2 alignment marks are made, you can unscrew the nut using a 15/16 socket
( counter-clockwise) and pull everything off the yoke.

If the 2 1/4 diameter on the gear end yoke( item # 1 ), where the oil seal rides, is not rusted or worn to badly, you can now just replace the oil seal ( item # 6 ) and the 3 1/2 x 1/8 o-ring ( item # 4 ). You can replace the seal and aluminum carrier
( item # 5 ) as an assembly or drive the old seal out of the aluminum carrier assembly and replace the seal only.

Before reassembly, you must now determine if the 2 large double bearings have a smaller 2 1/4 OD by 1 7/8 ID by 1/4 inch thick, inner spacer in-between them. If you do have the inner spacer, the bearings will easily slide off of the drive gear. If they do not slide off of the gear, they are pressed onto the gear ( do not force them off ). If they slide off easily, there has to be an outer spacer and an inner spacer which is used to set the pre-load on the double bearing package. Clean these bearings and reassemble all of the components, with the new yoke seal, in the reverse order from which you took them apart. Put a drop of loctite on the threads and place everything back in the vise and torque the 15/16 nut down to 80 foot pounds. Make sure after torque, that you can turn the double bearings by hand. There should be between 2 to 4 inch pounds of drag on used bearings and 6 to 10 inch pounds on new bearings.

If the bearings did not slide off of the gear, they are pressed onto the gear. Newer gear sets do not have an inner spacer to set the pre-load on the bearings. They use the 15/16 nut to draw the 2 bearings, which are pressed onto the .0015 oversized diameter, together. This is why you put 2 marks on the end of the yoke. You can reassemble all of the components, with the new seal, in the reverse order from which you took them apart. Put a drop of loctite on the threads and place them all back in the vise but DO NOT TORQUE THE 15/16 NUT because you will burn up the bearings. You must only tighten the nut back to the 2 alignment marks. Now lightly turn the bearings to see if you have 2 to 4 inch pounds to make the bearings turn. If they seem to loose, you can go past the 2 marks slightly to see if it makes them snug up a little. If you over tighten the nut, you will have to take everything apart and use a bearing separator to pull the last bearing away from the outer space slightly and start all over.

Once this is done, you can put the shims back inside of the hole in the upper housing and slide the engine driveline assembly back in. If you have a retainer nut wrench with the 1/2 square hole in the end of the handle, you can torque the 3 7/8 nut down to 120 foot pounds. The nut requires 200 pounds of torque, but if you multiply the length of the wrench it comes out to 120 foot pounds. If you do not have a wrench with the hole, you can hit the wrench a couple of times with a good sized hammer and it should be ok.

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