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  1. #1
    Join Date
    Nov 2008
    Location
    uk
    Posts
    66

    Default usual question-recommended prop size!

    Boat is a 22' sports type, probably weighing around 1.2 tons (weight of boat and trailer 1800 kilos) , motor is an early 80s Evinrude 90.
    Unloaded the motor spins happily up to +/- 6000rpm but underway the stern just digs down and we max out at about 5 knots and 2000 rpm.
    Current prop is stamped 13-3/4x15
    I accept that I may not have enough engine for the boat, but wondered if I can get some more performance with a lower pitch prop?
    Thanks in advance for any help.

  2. #2
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,707

    Default Re: usual question-recommended prop size!

    Run a compression test before spending $$ on a prop, 90 horse does sound underpowered, A lower pitch might get you more rpms,but hull might not plane off,wait for other responses,there will be plenty. Are your throttle plates opening all the way up, pull cowl and take a look.
    Last edited by johnnygjr; 01-24-2017 at 11:29 PM.

  3. #3
    Join Date
    Nov 2008
    Location
    uk
    Posts
    66

    Default Re: usual question-recommended prop size!

    Hi Johnny. Been through all the usual suspects (compression, carb settings etc.) to get her to run cleanly, which she's doing now. It's just a case of optimizing what I've got...

  4. #4
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,707

    Default Re: usual question-recommended prop size!

    As long as engine is within WOT and not aerating or cavitating "Slipping too much" she should be alright

  5. #5
    Join Date
    May 2011
    Location
    slough ,berkshire uk
    Posts
    155

    Default Re: usual question-recommended prop size!

    13.x13 to get it moving up the rev range, and do a proper lync n synce or youl never get moving.
    or simply vent the 15 pitch to make it at lie a 13 for the pull away.
    7/16th vent holes work nice.

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