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80HP Mercury Low Compression, Burned Piston Rings

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  • Ranger118
    started a topic 80HP Mercury Low Compression, Burned Piston Rings

    80HP Mercury Low Compression, Burned Piston Rings

    S/N: 7134777

    120 PSI on cylinder #1, #2, #4
    only 10 PSI on cylinder #3

    After open the powerhead, we can see #3 piston burned and the rings stuck on it, part of the ring missed.

    Click image for larger version

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  • orbanp
    replied
    Re: 80HP Mercury Low Compression, Burned Piston Rings

    You did not say what is the condition of the cylinder, but chances are that it needs a rebore. In that case, as jimmbo mentioned, you would need an oversize piston, and the link shows a standard size piston.
    Take your block to a machine shop who does two-stroke work, and they would be able to say if the cylinder can be saved.

    Peter

    Leave a comment:


  • CharlieB
    replied
    Re: 80HP Mercury Low Compression, Burned Piston Rings

    Clean that carb!!!!!!!!!!!!!! Or you will melt the next piston also.

    Anytime you freshen a motor, it is wise to kit all carbs, fuel pump, and water pump. Together, you are reducing the probability of things could go wrong and quickly destroy all that you have carefully rebuilt.

    Leave a comment:


  • Ranger118
    replied
    Re: 80HP Mercury Low Compression, Burned Piston Rings

    Thanks for the advice.

    Can we use this to replace the 6664A3 piston?
    http://www.iboats.com/2-Ring-Standar...view_id.173992

    Leave a comment:


  • jimmbo
    replied
    Re: 80HP Mercury Low Compression, Burned Piston Rings

    That piston is toast. Looking at it, I will assume the cylinder is scored. Have that cylinder bored oversize and get a piston, deglaze the others and re-ring those pistons. Don't forget to follow the break in proceedure

    Leave a comment:


  • Ranger118
    replied
    Re: 80HP Mercury Low Compression, Burned Piston Rings

    It's hard to remove the rings from piston.
    It looks like they melt and stuck together.

    What should we do next?
    Should we replace the whole thing or the rings only?
    How to to do a piston groove reshaping?


    Leave a comment:

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