?????? Question Johnson QD-16

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  • Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 3227
    Topics: 894
    #176222

    Who knows, maybe it will be a good runner when back together.
    Let us know what happens!
    I’ve never researched rings for a Scott yet.
    Possibly you could obtain some from this guy …….
    http://pistonrings.net/

    No sir that is the picture of a Scott Atwater model 497 …. May go ahead and clean the carb and fix the pull rope and see if it’ll start

    Prepare to be boarded!

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    wbeaton

    Canada Member - 1 Year
    Replies: 687
    Topics: 74
    #176343

    I think you are looking for a problem that may not exist. The fact that every motor reads 50 psi is a red flag. I have never seen a 1950’s OMC with compression below 60 psi that would run. In fact, 60 psi seems to be the basement of whether it will run or not. I’d prefer to see 70 psi or better. Every gauge reads differently, but the difference shouldn’t be that big. I suspect your gauge is reading low or not sealing properly. Either way, don’t start tearing things apart, yet. Start with the basics first.

    Wayne
    Upper Canada Chapter

    uccaomci.com

    Mumbles
    Mumbles

    Canada Member - 2 Years
    Replies: 4212
    Topics: 425
    #176353

    What Wayne says, X 2.

    phil
    phil

    US Member - 2 Years
    Replies: 106
    Topics: 14
    #176373

    He wrote:

    I have a 30 hp mariner on my boat that runs great and it shows 85 psi per cylinder so I’m thinking my gauge is ok.

    http://www.omc-boats.org
    http://www.aerocraft-boats.org

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    wbeaton

    Canada Member - 1 Year
    Replies: 687
    Topics: 74
    #176375

    I missed the 85 psi part on the Mariner. However, 85 psi is still low for a motor of that horsepower and age. I still suspect the gauge.

    Wayne
    Upper Canada Chapter

    uccaomci.com

    David Bartlett
    David Bartlett

    US Member - 1 Year
    Replies: 183
    Topics: 8
    #176378

    I missed the 85 psi part on the Mariner. However, 85 psi is still low for a motor of that horsepower and age. I still suspect the gauge.

    Especially if it runs well.

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    jeff-register

    US Member - 1 Year
    Replies: 1133
    Topics: 47
    #176386

    Looks like you have the pistons out. Take a ring off & put it in the cylinder & measure the ring gap at the top of the bore, next do the bottom of the bore to check for cylinder taper.

    tinkerman
    tinkerman

    US Member - 1 Year
    Replies: 105
    Topics: 18
    #176404

    No I didn’t take the pistons out yet, I was contemplating it. I think I’ll get a better compression gauge and see what happens. It makes sense if my mariner runs like a brand new engine then 85 is really low for that motor. It’s an 89 model. So maybe if the mariner is actually better compression than the gauge is showing (even 110-115) then maybe my vintage motors are closer to 80-90 which would be ok for an old motor. I wasn’t crazy about buying ANOTHER gauge but I think at this point I NEED to rule it out. Thanks for the advice

    Happy is a place we visit from time to time, content is a place where we can spend our life

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