compression test on 95 Mariner 60hp motor

  • Mr. Pike 81
    NW Iowa
    Posts: 192
    June 28, 2011 at 2:27 am #1238528

    This is a question for any Mercury mechanics or anyone else in the know. I have a 95 Mariner 60 that has compression of 105 on top 100 on middle and 105 on bottom cylinder. Seems low to me. Anyone know what it should be and if these numbers are cause for concern.Thanks for any info.

    BBKK
    IA
    Posts: 4033
    June 28, 2011 at 2:34 am #976649

    well, yeah that does sound low. It should be around 125-130 IMO

    Jesse Krook
    Y.M.H.
    Posts: 6403
    June 28, 2011 at 2:35 am #976650

    Quote:

    well, yeah that does sound low. It should be around 125-130 IMO

    X2

    stuwest
    Elmwood, WI
    Posts: 2254
    June 28, 2011 at 4:25 am #976663

    It does sound low. I suspect you have sticky rings. The good news is that the readings are even and the engine can probably be retrieved.

    What I’d do is to get some BRP Engine Tuner spray foam. Comes in a ~14oz aerosol can.
    Spray it in each cylinder after pulling the plugs.
    Let it sit overnite and repeat three days in a row, rolling the engine over 5 times each day.
    Run it out.
    Re run compression tests.
    I’m guessing you’ll go to 125 to 130.

    I’m getting jumps of 25# to 40# and I think the stuff is miracle juice!! We used to run ATF at about 25%, but that took forever.

    I’m going to be running it at least once a season on all of our 2 cycles and probably our 4 cycles as well, at least the carbuerated ones.

    Mr. Pike 81
    NW Iowa
    Posts: 192
    June 28, 2011 at 11:11 am #976676

    Thanks Stu. I’ll give it a try. The motor has been used to troll with a lot so that could be whats going on.

    joshbjork
    Center of Iowa
    Posts: 727
    June 28, 2011 at 1:55 pm #976732

    Quote:

    This is a question for any Mercury mechanics or anyone else in the know. I have a 95 Mariner 60 that has compression of 105 on top 100 on middle and 105 on bottom cylinder. Seems low to me. Anyone know what it should be and if these numbers are cause for concern.Thanks for any info.

    No, the numbers are borderline irrelevant. All you are looking for is a over like 90# and consistency. You can make the numbers go up by doing various things. It doesn’t matter at all. You’re just making sure one tire isn’t flat.

    millerman
    Red Wing, MN
    Posts: 627
    June 28, 2011 at 2:16 pm #976751

    Yes the perfect motor will be around the 130#. But the key thing is that they are within 5% which yours are. Go to a Yamaha dealer and get some ring free it works pretty good. although it really isn’t a problem if it runs ok where it is at. I worked on my cousins 150 VRO and it only had 95 to 100 lbs and that ran awesome! Also you want to run a good quality fuel and a good quality injector oil!

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