Still chasing leaks

[Efini Motorsport]

After about a year and a half of work I've finally been able to get my boat in the water. I'm still trying to work out some kinks but each time out it gets a little bit better. One of the bigger issues I have right now is that I'm chasing leaks. The first one I found (and dealt with) was leaks in the holes for the exhaust flappers. I'm pretty sure the remaining leak is through the gimbal housing. I've had the drive (two of them) on and off probably dozen times. Luckily my engine alignment is spot on and I can pull the drive in about 10 minutes. The first time ad the around I used the stock paper gasket and it leaked pretty bad. Since then I've swapped to a 1/32" silicone gasket with aviation gasket adhesive. It slowed it way down but I'm still getting water in the gimbal housing. When I pull the drive there's some water in the boot and the bearing is wet. When everything was apart I painted the drive and helmet. I didn't paint the mating surface of the drive and have scraped off everything on the mating surface of the helmet. The bellows and gimbal bearing were replaced when everything was apart too. I haven't pulled the drive off since I had it in the water today. I slowed the leak way down but I was still getting some water in the bilge. If I did manage to stop water coming in through the gimbal what should I check next?

 

[alldodge]

When I pull the drive there's some water in the boot and the bearing is wet.

Your boot is leaking, either the new boot has a crack or the sealing surfaces and either end. Could also be the housing but that should be able to be seen

 

[Efini Motorsport]

You're probably right about the boot. Guess I get to pull the drive again.

 

[Lou C]

With the Cobra boot there are a few cautions:

use an OE one if you can get it because they fit better and last longer (I have had them last as long as 10 years before small cracks appeared still no leak)

make sure the sealing surface of the gimbal housing is in good shape

make sure the rib in the sealing surface of the bellows fits into the groove of the gimble housing flange

i used OMC gasket sealer on the flange and the end that pops into the pivot housing

the paper gasket won’t cause a leak into the driveshaft bellow area but will cause deposits to build up behind the bell crank in the pivot housing....

i have heard if that grease tube tube causing a leak there but not a common problem

 

[Efini Motorsport]

That's why I use the silicone gasket instead of the paper. It seals great as it "oozes" just slightly to fill in irregularities in the surface. I've used it a bunch in automotive stuff including boosted supercharger applications. The best part is it doesn't get torn up if you have to pull the parts back apart

 

[Lou C]

With the paper gaskets I coat them on both sides with OMC gasket sealer and also coat the sealing surfaces of the drive & pivot housing and the 6 studs with it too. This is all mentioned in the OMC shop manual and I’ve never had leaks myself even though my boat has been moored in salt water every season 15 years worth in salt water.

 

[Efini Motorsport]

That's pretty much what I did with the aviation gasket adhesive. I'm going to check the gimbal bellow to make sure there's no rips. I may still have a slight leak in the exhaust too. It's just hard to see anything because the engine is so tight in the hole.

 

[kpg7121]

That's why I use the silicone gasket instead of the paper. It seals great as it "oozes" just slightly to fill in irregularities in the surface. I've used it a bunch in automotive stuff including boosted supercharger applications. The best part is it doesn't get torn up if you have to pull the parts back apart

Get rid of the silicone gasket & use Permatex liquid gasket sealer & I'll bet your leak will stop. How is that silicone supposed to cure properly when it's under water?

 

[alldodge]

No opinion for OMC, but Alpha get put together dry (bell to drive) and none have leaked