Johnson 1985 8hp motor lower unit leak/repair

[ba_50]

Hi,

My 8hp lower unit leaks oil out the bottom edge of the yellow plastic block the impeller plate sits on. Do I have to take this plastic block off and repair the seals? My manual doesn't show this type of block and it doesn't want to come off without possibly damagaing it.

Thanks. Bob

[Vic.S]

THIS DIAGRAM from the BRP website shows the all the parts but I would think the leak is more likely to be the gasket, item 14. The seals, item 27 would leak oil into the water pump housing and/or water into the gear case.

Note which way round the seals fit.

If you're are going to work on the lower unit it's worth replacing the prop shaft seals, items 2 and 3 as well and all the gaskets and O rings you disturb

[ba_50]

Vic,

If the gear oil isn't coming through the seals, where would it come from? I could drain the gearcase and look for water. That should answer one question. Thanks.

THIS DIAGRAM from the BRP website shows the all the parts but I would think the leak is more likely to be the gasket, item 14. The seals, item 27 would leak oil into the water pump housing and/or water into the gear case.

Note which way round the seals fit.

If you're are going to work on the lower unit it's worth replacing the prop shaft seals, items 2 and 3 as well and all the gaskets and O rings you disturb

[Vic.S]

Any place were oil is leaking out is also likely to allow water in. I did not mean to imply that ingress of water would necessarily point to the seals The most usual place for water to enter is via the prop shaft seals as they are the most likely to become damaged, eg. by fishing line. You will notice from the diagrams that at both places there are two seals facing in opposite directions. That is because the outer one is intended to keep water out while the inner one keeps the oil in. It only needs the outer one on say the propshaft to become worn or damaged and water will get in there but oil does not escape unless the inner one is defective. The same will apply to the two seals on the drive shaft, below the water pump but being relaively well protected they are much less like to be the cause of problems.

I felt that from your description of the location of the oil leak that it was more likely that it was the gasket, item 14 in the diagram, that was causing your oil leak. It will almost certainly be allowing water into the gear case as well.

I assume that the plastic block you refer to is item 25 which is called "Gearcase cover and seal" It is in effect the top of the gear case. It has oil below it and water above it.

It is difficult to know why that gasket is leaking oil, maybe it has been disturbed sometime in the past and reused instead of being replaced.

It should not be difficult to gently lever the "plastic block" out without damaging it once all seven bolts through it are removed. It is a fairly solid lump, not particularly fragile. The shift rod, item 39 will lift away with it so you will need to take care when rebuilding that it engages correctly with the cam, item 29.

[ba_50]

Vic,

Thanks for the very good description of how it works. I pulled the driveshaft out and could see the oil in there. That's different then the others I've worked on.

The gasket does need replaced. None of the seals have been replaced since it was new and we have used it a lot. I'm thinking about replacing them. I've ever done prop shaft seals before as I never had the right tools. Maybe this one is easier. I'll check it out. Thanks again. Bob

[Vic.S]

No special tools required.

While you have the lower unit off it might be worth also taking off the power head and having a look at the grommet at the top of the water tube.

See the pics I posted a link to recently at http://forums.iboats.com/bbBoard.cgi...59#gpid1173759

[ba_50]

Vic,

I noticed an O-ring on the parts list and mine is missing. Does it go inside the pump or just sit on top of it around the drive shaft?

Do you know what size it is?

I replaced the dirveshaft seals. Thanks. Bob

[Vic.S]

I assume you mean item 55 in the diagram (Part number 0303191)

It is located in the top of the water pump housing to make a seal between the housing and the shaft. Without it you will get very poor pump performance and it won't do any good just sitting on top of the housing.

Take a closer look you will probably find it is in there. I don't specifically remember it from the times I have stripped mine down so I probably did not renew it but it would be sensible to do so even if it is there and looks ok

I cant help with the size.