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  1. #1

    Default Under performance under load

    I have an 87 Supra Ski with the ford windsor 351 in it. Two years ago i started to loose compression so we rebuilt it. It now runs great and the compression is good. When i run it out of the water i get response on RPMs, but when in the water i can only get about 3200 RPMs when i open her up all the way. What could be causing it to preform bad under load?

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,824

    Default Re: Under performance under load

    Welcome aboard!

    First off, may I suggest just one post vs multiple ones.....

    I'd make sure the timing advance is functioning correctly first....

  3. #3

    Default Re: Under performance under load

    Makomark,

    We have checked the timing a few times, but I will check it again. Any pointers on making sure its perfect? Also we put a more aggressive Cam in when we rebuilt, would this cause a change in the timing?
    Thanks.

  4. #4
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,218

    Default Re: Under performance under load

    Ayuh,.... Ya probably got the same problem that burnt the motor down,...

    Bad fuel, or Bad fuel flow, causin' a lean condition,....
    Any Grease is Better,... Than No grease at All....

  5. #5
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,824

    Default Re: Under performance under load

    "checking the timing" isn't the same thing as verifying the timing advance.....

    And the caution offered by Bondo is due consideration as well...I can't tell you about the cam change driven impacts without knowing the details of the rest of the engine....

  6. #6
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,605

    Default Re: Under performance under load

    when i open her up all the way. What could be causing it to preform bad under load?

    1) re: more aggressive cam. A marine cam??? Engines in marine applications are "torque" hogs and need cams with broader torque peaks. Not knowing what that new cam does is problematic. You may have shot yourself in the foot with the cam change.

    2) Before you lost compression and performance, what WOT RPM did you get? Was the prop changed?

    3) re: "loosing compression" what % of maximum WOT RPM did you normally run at.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

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