water in lower unit

[jwilkey84]

I have a 1983 50 hp johnson. I just bought a lower unit for it last year that was supposedly rebuilt and pressure tested. Well I noticed some oil seeping out of a "vent" hole near the top of the LU, and I thought it was just from the expansion of the oil due to high temps here in iowa in june. Well I wiped it off and noticed it on a cooler day as well. I just took the top screw out of the LU oil cavity and the oil was full and looked new. Then I took the lower screw out and a little water came out and the oil was a milky consistency. I know I need to get this fixed, but can I just put a little new oil in it every time I use it and get by till fall? I have tinkered on motors here and there but I have never replaced seals on a LU. Should I start with just replacing the small gaskets where the oil fill screws are? Where is the problem usually when a LU is leaking slightly? Since this was rebuilt, and I really do beleive it was, which seals should I check first? Thanks, you guys are awesome and always a help to me. BTW does it take special tools to put new seals in the LU?

 

[wilde1j]

Re: water in lower unit

To test the LU for leaks:
1) Drain the gear oil
2) Pressurize to no more than 15 psig
3) A good LU should hold some pressure for 45 minutes
4) If the pressure test is OK, do a vacuum test
5) Should hold some vacuum for 30 minutes
6) If either test fails, the LU needs at least one seal
7) To find the bad seal, pressurize and submerge the LU
8) Bubbles will point to bad seal location (can be prop shaft, drive shaft, shift rod)

To do the test, you need an adapter to screw into the fill or drain hole, a 0-20 psig gauge and a vacuum gauge, suitable fittings and a Schrader valve or a manual block valve for the pressure/vacuum connection. Ebay has made up deals for under $75 from time to time.

For seal install, consult a shop manual. Some prop shaft seals may be installed w/o disassembly.

 

[Solittle]

Re: water in lower unit

I would replace the gaskets or seals for the fill & drain plugs - change the oil and retest before I went through all the rest of the tests. The gaskets are the most common source of water intrusion.

 

[jwilkey84]

Re: water in lower unit

I'll try that first, it's cheap and easy! Other than that, ther is a seal behind the prop and a seal around the impeller housing; is there any more seals?