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Compression Test Results

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  • Compression Test Results

    I have a 1988 150 ETLG, runs fine however, there is some loss of power compared with years ago (like it doesn't pull up heavier skiers like it use to, slower to plane out when boat is loaded....). Also some vibration noise at around 3000 RPM goes away at higher and lower RPMs. Compression test results are:

    Cylinder 1 - 95 psi
    Cylinder 2 - 96 psi
    Cylinder 3 - 100 psi
    Cylinder 4 - 95 psi
    Cylinder 5 - 103 psi
    Cylinder 6 - 105 psi

    I checked the accuracy of the test gage against a calibrated gage. I also decarbed before doing the above tests, no real signficant change in any after. I was consider going into the power head for check out and see if new rings, bore, or other was needed. Any comments on compression test results or friendly advices.


  • #2
    The compression readings are within specs.
    The compression on a V6 should be within 10% of each other and it will be different from top to bottom. Compare cyl.1 and cyl.2, cyl.3 and cyl.4, cyl.5 and cyl.6.
    Yamaha makes a fuel additive called "RINGFREE" that you can use. use the Shock treatment to help even up compression.
    You might want to get the fuel system checked out make sure carbs are clean and syncronized. the prop can also cause it to be hard to plane