Gear case pressure testing

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This topic contains 18 replies, has 6 voices, and was last updated by Avatar Tinman 6 months ago.

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    Tinman
    US Member - 1 Year
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    Topics: 18
    #163239

    How do you go about pressure testing a gear case? I hear a lot of talk about it and would like to learn how. How many psi are required and are there tools that can be purchased to do this or are most of the testers home made? Thanks!!

    fisherman6
    fisherman6
    US Member - 2 Years
    Replies: 1743
    Topics: 39
    #163379

    Tinman, there are commercially available pressure testers and many use them. Stevens instrument makes an excellent pressure tester as well as a vacuum tester. Some have adapted radiator pressure testers to work with gearcases with good results. Some of us use home made testers. Mine is a tester I made myself in my shop. It uses a 0-15psi gauge, a Schrader valve, and a machined aluminum body that screws into and seals against the drain plug hole. Testing is normally done between 6 and 10psi. Below is a link to a video I recently made in a series showing the tune up of a 1959 Evinrude Fastwin. I hope this helps.
    -Ben

    OldJohnnyRude on YouTube

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    Tinman
    US Member - 1 Year
    Replies: 110
    Topics: 18
    #163398

    thanks i appreciate the help! may try and make one myself. going to watch the video now. I have found no easy way to remove the seals, so why do it if you dont have to!

    Avatar
    crosbyman
    Canada Member - 1 Year
    Replies: 1204
    Topics: 158
    #163429

    gee.. optical illusion…. the front of that gearcase looks badly cracked ???

    fisherman6
    fisherman6
    US Member - 2 Years
    Replies: 1743
    Topics: 39
    #163687

    gee.. optical illusion…. the front of that gearcase looks badly cracked ???

    I think what looks like a crack in the front of the gearcase in the video is just sealer that squeezed out and tyat atring of sealer got dragged down from the seam of the case. I assure you there are no cracks in this one.
    -Ben

    OldJohnnyRude on YouTube

    fisherman6
    fisherman6
    US Member - 2 Years
    Replies: 1743
    Topics: 39
    #163688

    Old seals can be problematic to remove. They seem to get easier after you pull a few dozen and get the hang of getting them out. Still, there are stubborn ones that present a challenge. Ben Dittmar recently made a few videos showing how he gets seals out of the OMC gearcases. He does it very much the same way I do.
    -Ben

    OldJohnnyRude on YouTube

    • This reply was modified 6 months ago by fisherman6 fisherman6.
    Avatar
    Tinman
    US Member - 1 Year
    Replies: 110
    Topics: 18
    #163704

    Good videos. I’ll try that approach! Hopefully I don’t break anything! Lol.

    Avatar
    fleetwin
    US Member - 2 Years
    Replies: 2669
    Topics: 32
    #163718

    Good videos. I’ll try that approach! Hopefully I don’t break anything! Lol.

    Tinman
    I agree with you for the most part…..If there is no water present during routine gear lube changes, don’t go looking for trouble…. And yes, removing some of the seals/shift rod orings can be difficult, you run the risk of damaging castings by prying with inappropriate tools or using too much force.
    A pressure tester can surely be “home made”, but again, it is easy to get fooled by testers that have their own leakage problems….In other words, you may go looking for “gearcase leaks” that are really just faulty/leaky testers.
    It is always a great idea to submerge the gearcase in water during a pressure test so you can see exactly where the leak is coming from. Never just disassemble a leaky gearcase before trying to pinpoint the actual leak(s) using a pressure tester.
    Generally speaking, vacuum tests are usually only done on later style gearcases with “back to back” lip seals.
    What type of engine/gearcase are you concerned about? The old style OMC two piece “clam shell” gearcases are relatively easy to work on, but not all that easy to seal up properly.
    So again, I agree with you, don’t go looking for problems if your gear lube appears to be free of water. The best idea is to check/change gear lube frequently to catch little leaks before they become major and damage/destroy your gearcase.

    Avatar
    crosbyman
    Canada Member - 1 Year
    Replies: 1204
    Topics: 158
    #163729

    In the book CHEAP OUTBOARDS.. the author suggest that changing oil during the season is probably the best thing to do unless one wishes to go all the way with a reseal.

    I have done a few and it is not that hard but really….a lot of boaters will use their boats 50-75 hours per season so changing the oil in the old kicker won’t cost much with Wally mart oils and takes 15 minutes.

    you can buy a fair quantity of bulk 90w oil for the price of the drive shaft and prop seals ….

    Of course if the leak is very serious go for it …… lots of utubes to teach you

    if you live in snow country… make certain to drain and refill before the cold temps come in

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4107
    Topics: 420
    #163730

    If you don’t have all the necessary tools, there’s an alternative way to check for leaky seals. All you need is a spritzer bottle with some soapy water in it and an air supply. It doesn’t matter if it’s regulated from your compressor or from a few pumps with a bicycle pump, as long as it can deliver at least five PSI, which is probably more than the gearcase can develop while it’s in operation. Too much air pressure might flip an old seals lip inside out making an unnecessary teardown mandatory.

    All you have to do is drain the oil thoroughly and reinstall the drain/fill plugs securely before spraying the soapy solution on the driveshaft, prop shaft, and shift rod seals along with anywhere else oil could leak out. Any leaks will show as bubbles or foam around the leaky area.

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    Tinman
    US Member - 1 Year
    Replies: 110
    Topics: 18
    #163744

    thanks everyone for the good ideas. Pressurizing the gearcase and using bubbles is a great idea. Should of thought of that one myself. I am a hvac tech and regularly use soap bubbles to test for gas and refrigerant leaks. Is the thread size on the drain and fill plug a standard size? Thanks for all the help!

    Bryan

    Avatar
    Tinman
    US Member - 1 Year
    Replies: 110
    Topics: 18
    #163745

    Most of my motors are 1950’s johnsons and evinrudes. And we finally got some snow here in central missouri!!! Almost forgot what it looked like since we did not get any last year.

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4107
    Topics: 420
    #163780

    Is the thread size on the drain and fill plug a standard size?

    Yup, standard 3/8 – 16 UNC.

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4107
    Topics: 420
    #163781

    And we finally got some snow here in central Missouri!!!

    Snow? What’s that?

    Every year around the middle of January, I notice the days are getting longer and the daffs are starting to poke their heads out. I even got to mow a little bit of lawn yesterday!

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4107
    Topics: 420
    #163784

    Here’s the proof! ☺

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