1976 Johnson 20hp compression numbers

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  • September 21, 2015 at 10:41 pm #2600
    wiscoboater
    Participant

      Hi guys,
      I tested my odd ball tri wing 76 Johnson today. This motor has been sitting for a lot of years. I got 95 on the top, 101 on the bottom. This was without doing anything to it, nothing sprayed in the cold dry cylinders. Is this in the ball park for this motor?

      September 22, 2015 at 12:02 am #24348
      frankr
      Participant

        US MEMBER PAY BY CHECK

        Since the numbers are not published, it is save to guess is it is fine.

        September 23, 2015 at 11:38 pm #24472
        johnyrude200
        Participant

          if you spray fogging oil in there, I’ve seen very good shape 18-20-25 motors climb as high as 165PSI (!!!), whereas worn out ones, even with the help of the oil, may only get as high as 110-115.

          For what it’s worth I like to see pre and post fogging numbers to give me a little bit of insight as to ring/piston/cylinder health. If the numbers climb by 20-30 points, chances are it’s in good shape. If there is little rise, well you know you have wear.

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