Gear oil check valve seal Alpha 1 gen 2 drive

[khe]

I have a small gear oil leak in my Alpha 1 gen 2 drive that has been a real pain to locate. I noticed it last fall as a small spot on the driveway the size of a quarter. The anode on the front of the drive was stained with oil. It was blue/green so I know it's gear oil.

I pulled the drive prior to putting the boat in storage so I could inspect it and pressure test it. There was no water in the U-joint bellows and when I drained the gear oil, there was no water in the oil. I pressure tested the drive a week ago and it passed. I sprayed brake clean around the shift shaft seal in the gimbal housing and it did not leak past the seal. I did notice some slop (1/32") between the shift shaft seal and the lower brass bushing in the gimbal housing but that would only leak water into the exhaust cavity and the Mercruiser parts diagram doesn't show a seal in that area.

The gear oil hose from the reservoir was replaced about four years ago and there was no oil residue on it at the gimbal housing.

I inspected the lip seal on the drive that retains the spring and ball that depresses the check valve on the gimbal housing and noticed some nicks but they are not on the sealing surface as the seal is 1/32" recessed in the drive and the check valve is recessed into the gimbal housing by the same amount. The sealing the seal accomplishes is via the lips and they don't appear to be damaged. A picture of the seal is attached.

Is there anything I am overlooking? I don't know what to check next and I certainly don't want to throw parts at it in hope that I would fix it.

Thanks!

 

[achris]

What pressure did you use when you tested the drive?

Most people use 10 to 15 psi. If a seal has relaxed, that's enough pressure to force it closed, and the drive will pass the test. But there isn't that much pressure in the drive normally. I test at 2 different pressures, initially 2 to 5 psi, then the higher pressure. 2 to 5 psi will pinpoint a weak seal...

Chris....

 

[khe]

I used 10 psi for the pressure test. I made a pressure tester and used the plastic fitting (with an added o-ring and teflon tape on the threads) from the gear oil pump I had. It leaked down to 2 psi over a few days and held.

I then bought another gear oil pump with a metal fitting and o-ring and pressure tested the drive to 10 psi and it held.

The seal in the picture doesn't look right to me. I normally don't "throw parts" at a problem but the replacement seal, spring and ball bearing "kit" was $7.00 at the marina and I figured what the heck - the drive is already off, I might as well replace it.

 

[khe]

It has been one week since I changed the seal in the picture above and installed the drive. So far, there are no leaks.