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Volvo Penta AQ131D compression problem

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  • Volvo Penta AQ131D compression problem

    I tested the compression on the motor this weekend and found my rough idle culprit. Here's the results.

    Cylinder 1: 3psi
    Cylinder 2: 150psi
    Cylinder 3: 120psi
    Cylinder 4: 150psi

    #1 is a real problem, I'm thinking a broken valve or something
    #3 is probably worn piston rings, valve seating issues or something.

    This is outside my area of expertise and I lack the special tools to perform this work. Does anyone know a reasonable shop in the southwestern Ontario area that could do this type of work? Can I take it to a regular mechanic or does it have to go to a marine shop?

    Any idea what type of price tag I'd be looking at?


  • #2
    I took the opportunity to remove the intake and exhaust manifolds this weekend to have a look. The exhaust side looks okay. The intake side looks carboned up so I'm thinking it's not sealing. Not sure what to do with this information now but it's interesting. All the valves move when I hand crank the belt drive however I cant move it too much before things tighten up.


    • #3
      I would check to see if the timing belt jumped a tooth.
      This can cause compression problems and is easy to fix.

      Valves may appear to move, but it is difficult to see if they fully close or seal.
      20' 1987 Renken Cuddy Cabin
      AQ131C 270 drive
      Southern NJ


      • #4
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        Thanks, a mechanic buddy of mine suggested that because of the carbon and oil deposits in the intake he thinks it's likely a head gasket issue which is probably my best case scenario. He agreed that its difficult to tell if they close properly without pulling the head so I guess I'm playing mechanic for a bit. He gave me pointers on how to position the pulleys so we can get it back together without issues.

        The timing belt slipping a tooth I cant see causing compression issues on only 1 cylinder after considering it.