lower unit seals

Is this the only seal that usually goes out, besides the gaskets on the fill and drain plugs. My problem is, This 1969 motor has sat for who knows how long, it is still full of lower unit oil and there is no sign of seal leakage. I pulled off the prop and there is even cosmoline still on the shaft. I sure looks like all I would have to do to change the seal is pull off that bearing retainer and press out the seal and install a new one. Or, should I run it and watch it for leakage.

Re: lower unit seals

If it ain't broke, don't fix it. If you are concerned, then consider pressure testing. If you don't have the pressure, and vacuum testing equipment, you could drain the gearcase and have the local dealership test it for you. Just make it as convienient as possible for them to test it (completely drained, with one plug removed) and the charge will be minimal. Or you could run it a couple of times, and drain the oil and look for traces of water.

Hope this helps, Jimmy

Re: lower unit seals

You don't say what motor but usually there are two seals on the prop shaft, fitted back to back. One keeps the oil in the other keeps the water out,

Similarly there are seals on the drive shaft where it enters the gearcase below the water pump.

There is also a seal, or at least an O ring on the shift rod.

If it has sat for a long time then it would be prudent to change the water pump impeller. While doing that is the time to do the drive shaft seals and the shift rod seal if they need changing.

Maybe a good plan is to run it for a while and then check for water entering the gearcase. Then do the pump impeller and the seals at the same time if needed or as a precaution.


See "Awakening a sleeping outboard" in the Engine FAQs

Re: lower unit seals

If you pulled the drain and vent plugs and you found normal oil, then I would fill it, run it in fresh water, and check it again after a few runs. If you see evidence of leaking then, change out all the seals. If you don't, let it be. I had a 1960 10 HP Seahorse. It had sat for at least 10 years in someone's basement, and for an entire winter outside. The lower unit didn't leak at all. . My understanding is that even with a leak in the lower unit, the oil is designed to keep things lubricated and protected, as long as its attended to in a reasonable amount of time.

-Eric