Gearcase leak…where? how?

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  • nj-boatbuilder57


    Replies: 284
    Topics: 41
    #248189

    My season is over, and as a matter of habit, I always drop my lower before I put everything away. Years back I learned the hard way: trapped water froze, expanded & cracked a housing. Since dropping & draining is a 10 minute job, I long ago decided “why not”? It’s just part of my winter storag procedures.

    Anyway, this year, along with about a cup of water, I was greeted with a foamy green slime in the impeller housing area….I figured “water in the gear oil”, so I drained it. (It was new oil & pressure tested in March before I launched)

    null

    This is a sample of the gear oil I used (West Marine 80W-90), dark green, on the right. On the left is what I drained out. In years past, my drained oil looked good enough to reuse. This year…nope! This looks like water got in, right?

    null

    Here’s the part that has me confused: I figured I had to find out where it’s leaking, so I did a pressure test. My gearcase has been holding 4PSI for an hour now. I can turn the shaft, manipulate the shifter, etc. and the gauge remains at 4PSI.

    null

    But it also occurs to me: keeping pressure *IN* doesn’t automatically mean the unit can keep pressure *OUT*….but what other means do I have to test / verify? I have no pressure chamber to verify the ability of the unit to keep pressure out.

    Still, 4PSI is about 9 feet of water, so I would like to think that any seal that could handle 9′ H2O in one direction could surely handle the pressure associated with the immersion depth this is exposed to in normal operations. Or maybe not. Anyway, it sure looks like water got in, right?

    Or should I just put in clean oil, seal it up and wait for next season? Do I need to split the gearcase / skeg and clean everything?


    RICK EICHRODT

    US Member - 2 Years
    Replies: 230
    Topics: 64
    #248196

    You might bump the pressure up to say 8 to 10spsi. Then submerse the lower unit into a bucket of water or use a spray bottle filled with dish soap and water. Either way, look for air bubbles coming out from somewhere? If it is coming from under the water pump plate, then that is a somewhat easy fix. If it is coming from the shift shaft seal, the entire gearcase needs to come apart again. If you have a tiny leak, you might get away with just refilling with clean oil and use it next year “as is”! If this is the way you decide to go, check the oil from time to time next year so see if the oil gets washed out.


    fleetwin

    US Member - 2 Years
    Replies: 4075
    Topics: 41
    #248197

    Well, you could do a vacuum test as well, but that was never recommended by OMC for these style gearcases…Until later years when “back to back” seals were used. One set of seal keeps oil from pushing out, the other set keeps water from pulling in… So, using a vacuum tester might just overcome the seals natural resistance and add even more confusion…
    Like others have said, it is always a help to do the pressure test in a bucket of clean water. It is not enough to just add pressure and watch the gage, you really need to move the shift shaft up and down, rotate the shafts while pulling them in and out… Doing all this while submerged in the water will show any stray bubbles…And, like others have said, bump the pressure up to 10PSI or so to check condition of orings. Finally, are you sure this isn’t just an issue of a missing or damaged seal washer used on the fill drain screws? Sometimes the screws get swapped, so there are two gaskets on one screw, and none on the other.
    In any event, the little bit of emulsion showing is not that big of a concern right now…I would not pull that thing apart until such time that you have found the actual leakage issue/problem or the leak gets much worse.
    Change the gear lube more often next season just to monitor the situation…


    rmhxruss

    US Member - 1 Year
    Replies: 135
    Topics: 5
    #248198

    Try 2 PSI to much air can make the seals work better.


    Mumbles

    Canada Member - 2 Years
    Replies: 5245
    Topics: 282
    #248202

    If you spray some soapy water on the seals, shift rod seal, and fill/drain plugs, it will help to isolate any leaks. Using low air pressure is better than high air pressure as too much pressure can force the seals lip against the shaft which will give a false no leak condition.

    Leaky-Drive-Shaft-Seal


    nj-boatbuilder57


    Replies: 284
    Topics: 41
    #248205

    one hour in a bucket at 11PSI…not a bubble to be seen… Manipulated the shifter, wiggled it a bit…turned the shaft, wiggled it a bit too. No bubbles at all.

    null

    1.) interesting note (above) about testing with lower, not higher, pressure. But I’m closed up for the day. I’ll try that tomorrow night.

    2.) when I initially put it in the bucket, I had bubbles where my hose fitting went into the housing. I had to tighten it quite a bit more than I would have suspected. This whole thing could have been as simple as a bad seal on the upper plug…

    3.) If re-testing with lower pressure doesn’t reveal anything, I’m ready to declare the seals to be OK and chalk this up to a bad seal on the plug.

    Am I missing anything?


    fleetwin

    US Member - 2 Years
    Replies: 4075
    Topics: 41
    #248216

    I don’t think so. Like others have said, the low pressure settings test the seals, the higher setting is for orings or the spaghetti seal…
    If it were mine, I would leave the drain plugs out for a few days with the gearcase tipped forward so the fill plug is at the lowest point in an effort to drain any left over emulsified gear lube out of there…
    Next, I would probe the threaded pockets where the drain/fill screws reside in the gearcase to make sure this isn’t a case of left over gaskets in there…Then use new OEM plug gaskets: 311598. Thread one new gasket/seal/washer onto each drain plug…
    Finally, you may want to consider using some of the better OEM lower unit lubes that are made to “absorb” a certain amount of water without losing much lubricating qualities.
    I definitely would not pull this thing apart…


    nj-boatbuilder57


    Replies: 284
    Topics: 41
    #248218

    It was raining when I wrote my previous post, but it stopped, so I went back outside & repeated the test at 2PSI. No bubbles at all…

    So I became convinced this must have been a fill port plug that wasn’t sealed well enough.

    But then I got to thinking: If there were water in my gearcase, that would be the limit of my issues. But I have this foamy wet oil up around the upper seal, so that made me think that was the spot where the leak was. I cleaned most of it out before I started taking pictures, but here’s an example:

    null

    So I re-pressurized and added soapy suds to the shaft seal and the shifter o-ring. Nothing. Not a bubble to be found. It’s not shown, but I lowered the pressure to 2PSI…still no bubbling. I’m a bit stumped.

    O-ring soapy…no bubbles:

    null

    Upper seal soapy…no bubbles

    null

    Thoughts?

    Or just re-fill with new oil & see how it goes next season?

    Also, there’s this:

    Finally, you may want to consider using some of the better OEM lower unit lubes that are made to “absorb” a certain amount of water without losing much lubricating qualities.

    I’m all ears. Any recommendations?


    billw

    US Member - 2 Years
    Replies: 1610
    Topics: 48
    #248224

    Could have been leaking by the gasket on the vent screw, which you have now removed to install the pressure tester. This is sometimes an occupation where strange things happen…..

    Long live American manufacturing!


    Buccaneer

    US Member - 1 Year
    Replies: 5195
    Topics: 840
    #248229

    I wished I had a motor sealed up that tight, lol.

    Prepare to be boarded!


    nj-boatbuilder57


    Replies: 284
    Topics: 41
    #248243

    If it was the seal on the vent plug, then how is this oil-water-foam getting up into the impeller housing? Any ideas? That’s the part that has me scratching my head…


    dave-bernard

    US Member - 2 Years
    Replies: 1495
    Topics: 19
    #248247

    that is unburnt fuel from the motor. not lower unit oil.


    crosbyman

    Canada Member - 2 Years
    Replies: 2344
    Topics: 240
    #248250

    had similar issue (foamy oil) on my 75hp ETEC last year . took the LU home for winter testing pressure tested 15 min at 12 psi and negative 10 psi Vacum for 10 min no leaks

    used new crush nylon washers when I filled it up and stored it last winter

    this season at bed time for winter last week I drained the oil….. NO WATER had come in the LU

    conclusion…. don’T reuse old crush nylon washers 🙂

    Joining AOMCI has priviledges 🙂


    billw

    US Member - 2 Years
    Replies: 1610
    Topics: 48
    #248252

    The stuff in the containers is out of the gear case itself, though, right?

    Long live American manufacturing!


    nj-boatbuilder57


    Replies: 284
    Topics: 41
    #248253

    In my first post, second photo: Yes….the light green stuff (center & left containers) is the oil I drained from the gear case. By contrast, the container on the right (dark green) is a sample of new oil from the same container that was used to fill the gear case in the spring.

    The sludgy stuff up around the impeller housing is fuel-oil residue? Very interesting. If I can rule that out, then this may be as simple as plug washers.

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