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Johnson 65esl72

Too DogsToo Dogs Posts: 6 Greenhorn
The lower unit was milky when I drained to check the gear case oil. I'd last changed in June of this year. There were no metal shavings, just the fresh water mixed into the oil and after a week, it did not separate. I do not fish salt water.

On the advice of a mechanic, I drained and changed the oil, then took it fishing. This time after 3 hours there was more water than before, maybe 25% and it separated out in 12 hours.

Today I made a new drain screw with a schrader valve so I could pressurize the gear case with a bike pump to 20#'s; manual recommends 16 to 18 but I wanted to make certain it would maintain the pressure and did not care if I blew a seal as I figured I'd be doing a re-seal anyway. After 3 hours, it's still at 20#.

Initially this spring I re-used the plastic drain screw gaskets.

Last time (25% leak) I used new OMC fiber gaskets.

For this last pressure test I found that new fiber gaskets did not seal the top drain screw so, after careful visual examination of the threads, screw and seat, I used OMC "O" ring for the top only; it did not leak under a soapy water mix(no bubbles) and is maintaining test pressure.

My question; Can/should I use an RTV sealant and O-ring when I refill with lube? Is there a surefire way to seal the screws? Is there anyway to know if I have a leak after filling w/oil, except by checking after an hour of use?

Does it sound like I do not have a seal leak, only a leak at the screws since the gear case is holding pressure w/o oil?

Is there something I am missing?

Thanks, Jerry in MI.


  • BillgranBillgran Posts: 350 Deckhand
    Not only does the gearcase need a pressure test, it also needs a vacuum test.

    Most likely your problem is the driveshaft seals but replacing both seals is not that big a deal.

    "There is never just one thing wrong with a boat"
    --- Travis McGee

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