Questions on a lower unit that has had some water in it.
Recently found the lower gear case full of water and resealed all seals and o-rings (all Mercury parts from local dealer) just a few weeks ago. Filled lower unit while level until gear oil just started to come out of the top plug. Since the reseal, I have noticed that I have a few drops of oil on the shop floor after running for the day. (Coming from the drain hole nearest the shift shaft) Wasn't sure if it was 2 stroke oil or oil from the lower unit so I put a dose of dye into the lower unit and ran it another day. Blacklight showed that the oil was coming from the lower unit. Leveled the gear case and took the upper plug out to ensure that it wasn't overfilled and just had a drop of oil coming from the hole. New oil also looks a little foamy so I'm thinking that I am still getting water into the gearcase.
I removed the lower unit again, drained and pressure tested along with some soapy water. The only bubbles that I had were around the shift shaft which is a single lip seal. Will this seal being a single lip still hold up to 12-14psi without leaking air past it? Everything that I have read online says to pressure test it and make sure that there are no leaks but wouldn't this seal open and vent out any pressure that may get built up inside the case? I'm only able to get a few psi on the case before it starts losing air past the seal.
* I did look over the shift shaft itself and it doesn't seem to have any noticable wear where the seal rides but I haven't put a micometer on it because I don't have any reference to the proper diameter.
* Is there anything that may be worn on the lower side of the upper shift lever (up inside motor housing where lower unit connects) that may have the shaft not properly aligned and pushing the shaft to one side of the seal and not having proper contact around the seal?
* Is there anything else that you can think of to check before putting a new shift shaft in it? If it's supposed to hold 14ish pressure, I'd assume that it would have to be the shaft itself that is worn.
I've got all the tooling to tear down and rebuild (except the pre-load tool for the drive shaft) but I'd guess that as long as I reuse the same shims, it should be close enough for a 25 year old lower unit. That tool is around 1/2 the cost of an aftermarket lower unit so the purchase of it is beyond what I'm willing to spend on this old lower unit.
Main question is should the shift shaft hold 14psi and I appreciate any help or suggestions that you have.
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