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How many rotations on a compression test?

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  • How many rotations on a compression test?

    Should the number of rotations be limited on a compression test?

    I've read crank it until the cylinder reads max pressure, and I've read to limit it to 6-8 rotations per cylinder, while watching how much pressure you get on each rotation.

    Which is the best method for outboard motors?
    Bob
    2003 Crest Super Fisher 25' Pontoon with Yamaha F90

  • #2
    I crank the motor until the pressure stops rising. Should not be more than five or six revolutions I would guess. Depends somewhat on the length of hose from the spark plug hole to the gauge.

    Battery fully charged. All plugs out. Throttle wide open. Motor hot. Kill switch activated to prevent a spark which could light up the air/fuel mix.

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    • #3
      Thanks boscoe99
      Bob
      2003 Crest Super Fisher 25' Pontoon with Yamaha F90

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      • #4
        I do six rotations, with wide open throttle,

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        • #5
          Thanks for the reply Sequoiha.
          Bob
          2003 Crest Super Fisher 25' Pontoon with Yamaha F90

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