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compression on looper engine

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  • compression on looper engine

    Hello I have a 1989 v6 johnson looper engine and was wondering what would be concidered good compression: I have 72-75 psi on all cyl but dont have the power I think it should -brought to marina -they striped spark plug hole, didnt tell me till later just said the engine is wore out . starts up good and idles fine it is on 19' statos bass boat with 14.5x26 prop top rpm was 3500 --changed prop to 14.25x17 4 blade and still only could get 4900 rpm any help is appreciated thank you
    Last edited by black1; July 16th, 2008, 03:30 PM. Reason: to complete question


  • #2
    Re: compression on looper engine

    Welcome to iboats. there are no published numbers. guide we use is ; over 100psi, but most important is that they are within 10% of each other. post your results, you will get opinions.
    FLORIDA GATORS
    TEBOW Country



    Please, NO PM's (Private Messages) regarding boat/engine problems. they will not be answered.
    That is what these forums are for. Post your questions, in the appropriate Forum.

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    • #3
      Re: compression on looper engine

      does that indicate a rebuild ?could i get away with rings and have the bores honed? thank you

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      • #4
        Re: compression on looper engine

        Originally posted by black1 View Post
        Hello I have a 1989 v6 johnson looper engine and was wondering what would be concidered good compression: I have 72-75 psi on all cyl but dont have the power I think it should -brought to marina -they striped spark plug hole, didnt tell me till later just said the engine is wore out . starts up good and idles fine it is on 19' statos bass boat with 14.5x26 prop top rpm was 3500 --changed prop to 14.25x17 4 blade and still only could get 4900 rpm any help is appreciated thank you
        Have you checked the compression on the engine? 72 - 75 is low, but I would expect the cylinders to be more than 3psi apart if it was indeed worn that far. All guages read different. Get a screw in compression tester that holds the reading and take all of the plugs out. Make sure the battery is fully charged and turn the engine over 4 or 5 revolutions on each cylinder until it reaches the highest reading. Then report back what you find.

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        • #5
          Re: compression on looper engine

          If the psi numbers are close and the engine runs well forget compression, Black1.

          I think you are still overpropped. What boat is it on?
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