lower unit test

Quick question.I resealed the top side and waterpump of my 1984 Johnson 90hp.I ran it on the muffs for a while checked my gear oil and it was good no water.So I feel comforatable everythings OK up there.Question is I havent had a chance to get to the lake this weekend like I wanted to what I am wondering is I have a old 120 quart cooler could I fill it up with water and lower the LU into it and let the motor soak for a few hours and be able to tell if I was getting some water intrusion at the prop shaft seals?I dont have any oil leaking around the seal or nothing I was just wanting to make sure no water was getting in..Also I mean to just tilt the motor down into the cooler and let it soak not start it or anything..

Re: lower unit test

I really don't think that would tell you anything. It needs to be ran a while (in gear) to be sure. You could have it pressure/vacuum tested.

Re: lower unit test

Agree, take her for a run.

Remove the drain screw, and notice the first bit of oil that exits. The water is heavier than the oil, and will sit at the bottom of the gearcase. IF there is still water intrusion, the first bit that exits will be milky white.

You will have to let the unit sit for a while to settle though. Or pressure test it as stated if you have the equipment.

To pressure/vacuum test a lower unit:

a) drain the gear oil
b) use an appropriate adapter with a gauge tee'd in to apply pressure or vacuum. No more than 15 psig for pressure. You can use a bicycle pump or any other compressed air source for pressure. For vacuum, you need a vacuum pump.
c) LU should retain some pressure or vacuum for 45 minutes minimum.
d) If pressure doesn't hold, submerge LU in water to find leak source [possibilities: drive shaft seal, prop shaft seal(s) (usually two), shift shaft seal and the fill/drain screw washers.]
e) replace offending seal(s) as required.