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  1. #1
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    Default How to pressure test an outdrive?

    About finished building my pressure tester. Seen a lot on the forums, but no procedure as to exactly what i'm looking for. I can't find it in the manual either...
    1) I assume just pump it up...to what PSI? for how long?
    2) Common leak points?
    3) Vacuum testing? yes or no? to what level?

    Thanks (I will NOT blow out another upper gear set this year

  2. #2
    Chief Petty Officer Black as's Avatar
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    Default Re: How to pressure test an outdrive?

    Quote Originally Posted by nola mike View Post
    About finished building my pressure tester. Seen a lot on the forums, but no procedure as to exactly what i'm looking for. I can't find it in the manual either...
    1) I assume just pump it up...to what PSI? for how long?
    2) Common leak points?
    3) Vacuum testing? yes or no? to what level?

    Thanks (I will NOT blow out another upper gear set this year
    If you go to about 10 psi you should be fine and use a spray bottle of soapy water to hi-light any leaks, bubbles will appear thats if you have a leaks at all

  3. #3
    Moderator achris's Avatar
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    Default Re: How to pressure test an outdrive?

    Go to the ADULTS ONLY thread at the top of this forum. Then choose option 9 (Pressure testing an outdrive).

    Or, if you're really lazy, click HERE.

    Chris
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  4. #4
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    Default Re: How to pressure test an outdrive?

    Quote Originally Posted by achris View Post
    Go to the ADULTS ONLY thread at the top of this forum. Then choose option 9 (Pressure testing an outdrive).

    Or, if you're really lazy, click HERE.

    Chris
    yeah, saw that before. more on building a tester than the actual testing. is there no procedure stating how long the drive should hold a particular pressure/vacuum?

  5. #5
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    Default Re: How to pressure test an outdrive?

    The manual for my Volvo outdrive is pretty specific about pressure and vacuum values and how long to hold each. Just need to convert metric to SAE if needed. Even the Seloc manual has the procedure.

  6. #6
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    Default Re: How to pressure test an outdrive?

    Anyone know if its in the merc manual anywhere?

  7. #7
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    Default Re: How to pressure test an outdrive?

    mike,
    The good thing (and something embarassing thing) about this forum is the related links feature below a thread. Looks like Don S. mentioned the lack of presure & vacuum test info in the Merc manual. But it looks like there are some values and times for your Merc outdrive in the rest of the posts.

    Good luck.

  8. #8
    Moderator achris's Avatar
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    Default Re: How to pressure test an outdrive?

    Quote Originally Posted by nola mike View Post
    yeah, saw that before. more on building a tester than the actual testing. is there no procedure stating how long the drive should hold a particular pressure/vacuum?
    Most techs pressure test to about 10-12psi for 30 minutes... Vacuum test to about 10-12" for 30 minutes. You should see no losses in that time...

    The only thing I've found is that the shift shaft seal on the MC1 to A1 gear housings sometimes leak at about 6psi, if they are a bit old.

    Chris..........
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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  9. #9
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    Default Re: How to pressure test an outdrive?

    ok, so pressure test @ 10 psi loses maybe 1/2 psi (or a little less) in 45 min or so. spraying everywhere doesn't reveal a leak. vacuum testing, i hear a leak at the input shaft at anything over 5 mm hg. while i'm not thrilled with this, it appears that the input shaft seal isn't designed to hold a vacuum. also, i'm thinking this is less of a concern, since it isn't exposed to water anyhow...i'm tempted to at least give the drive a shot, and keep a close eye on the gear lube.

  10. #10
    Fleet Admiral Gary H NC's Avatar
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    Default Re: How to pressure test an outdrive?

    I test mine at 12 to 14 psi... Let it set overnight and no pressure loss.
    The one manual i have states at least an hour.
    So i guess there are so many different opinions on this...


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  11. #11
    Master Chief Petty Officer bigskiohio's Avatar
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    Default Re: How to pressure test an outdrive?

    Last year i just checked mine and drained a little and fill before i go out everytime .yeah the oil is 15.00 a qt. . i bought two and have some left for this year. Alot of people never check after the first time and never realize the have water or lost oil and burn it up. Go by 10 seal/washers and change them everytime you check. especially the bottom one. I hear it all the time that we lost our oil all at once and killed the drive but was never checked before they went out.
    1973 Starcraft Supersport
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  12. #12
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    Default Re: How to pressure test an outdrive?

    Quote Originally Posted by nola mike View Post
    ok, so pressure test @ 10 psi loses maybe 1/2 psi (or a little less) in 45 min or so. spraying everywhere doesn't reveal a leak. vacuum testing, i hear a leak at the input shaft at anything over 5 mm hg. while i'm not thrilled with this, it appears that the input shaft seal isn't designed to hold a vacuum. also, i'm thinking this is less of a concern, since it isn't exposed to water anyhow...i'm tempted to at least give the drive a shot, and keep a close eye on the gear lube.
    Nola Mike,

    I'd say you have a problem that needs finding. If it doesn't hold vacuum it WILL suck water in.

    When you say 'input shaft' are you referring to the yoke at the front of the drive? If so, then that indicates the seal is faulty or the seal surface is grooved. It needs fixing!

    Chris........
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
    **
    Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
    **
    Member of the month - April 2013. http://www.iboats.com/blog/achris-member-of-the-month/

  13. #13
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    Default Re: How to pressure test an outdrive?

    Quote Originally Posted by achris View Post
    Nola Mike,

    I'd say you have a problem that needs finding. If it doesn't hold vacuum it WILL suck water in.

    When you say 'input shaft' are you referring to the yoke at the front of the drive? If so, then that indicates the seal is faulty or the seal surface is grooved. It needs fixing!

    Chris........
    boo. yes, that's what i'm referring to. now, looking through the archives, it appears that this seal will leak at some low value when vacuum is applied. is that not the case? and where would the water come from (barring a bellows leak?) lastly, how hard is this to fix? is it a matter of removing the retaining ring and replacing a seal, or is it more difficult than that? hard to tell from the diagrams, and i haven't done that before...

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