1956 Merc MK 30 H

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  • December 10, 2020 at 6:09 pm #224844
    terry wier
    Participant

      I just bought a 1956 Merc MK 30 H on contigent that the power head is in good shape. The motor was alledgedly restored 20 years ago ( looks pretty good) but has been sitting unused since. Here is my first issue (note: I have limited experience). In checking compression on #2 I get 89 lbs. When I put the gauge on #3 the motor locks up. It pulls fine without any plugs or gauge hooked up and pulls a little harder like you would expect with a plug in # 2 or #3. Put the gauge back on and it locks.

      The gauge I have definitely screws in a lot further on # 3 and I am pretty sure the piston is hitting the gauge. ??? I have not tried # 1 or # 4 yet as I need to take the upper and lower cowls off to get the pressure gauge hooked up.

      Any comments appreciated.

      December 10, 2020 at 6:22 pm #224849
      dave-bernard
      Participant

        US Member

        get a mercury gauge. +about $40.00 will work removing any cowls.

        December 10, 2020 at 8:53 pm #224862
        terry wier
        Participant

          Thanks for the reply. I looked at my gauge again and saw it had a built in longer coupler. I took that off and problem solved! Compression is good.

          December 11, 2020 at 3:09 pm #224958
          kirkp
          Participant

            Curious. Why could he crank the motor over with gauge in #2 but not in #3? Pistons rotated 180 deg? Also, why would it screw in farther on one cylinder?
            Kirk

            December 11, 2020 at 7:17 pm #224981
            terry wier
            Participant

              That is a mystery to me as well. Maybe I hit a rough thread spot on #2 and just didn’t tighten the gauge enough. When I retested with the shorter connector #2 was 106 vs 89.

              • This reply was modified 3 years, 4 months ago by terry wier.
              • This reply was modified 3 years, 4 months ago by terry wier.
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