Resealing 4.3l omc cobra lower

[jokey1]

I guys I have a Omc cobra lower unit and I have changed the seals. It is separted from the upper. I hook my air up and place it under water to look for bubbles. I pressure it to 15psi and then 30psi and no bubbles. When I go to vaccume check it I pump it down to 15hg and it does not hold it. I takes about 20 minutes to get to 0hg. I do not know how to find this vaccume leak. Do you guys have anytips? Also I used ulta grey silcone on all the seals except for the propshaft and shift rod. Does any one have objections to silcone? Thanks for your time.

 

[Don S]

Re: Resealing 4.3l omc cobra lower

Silly cone has no buisness on any seals on an outdrive. PERIOD.<br /><br />Your vacuum leak is probably at the input shaft seal. It's not designed to prevent water from coming in, so there is no lip to hold the vacuum.<br />Usually they will hold 7 or 8 inches of vac.<br />Just tilt the drive back and cover the seal with heavy gear lube and pull the vacuum. If it holds, you are good.

 

[jokey1]

Re: Resealing 4.3l omc cobra lower

Hello Don S I have the lower unit seperated from the upper. I used an rubber coupler for pvc with the associated fittings to hook up to the aircompressor and vaccume pump to the lower unit. The pvc rubber coupler is on were the drive shaft would be. I thought It would be ok to use silcone on the seal. I have used the ulta grey silcone to reseal engines and manual transmissions on cars and I never had a leak. The only leaks I have seen were when the sealing surface was not clean. I thought that a sealing a gear case with it would be no problem. Heck there is no high pressure or extream heat.