repowered boat prop help needed

Discussion in 'Props' started by get reel, Jun 26, 2019.

  1. get reel
    Joined: Jul 2010
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    Location: toledo ohio

    get reel Junior Member

    Ok I have repowered my 1989 BAHA 28ft weekender and need some help choosing the correct prop. as of now the current prop is a 4 blade 18 X 14 pitch . At WOT 4900 rpm I'm running at 23 knots . Boat is around 8500lb transmission is 1.88 gear straight drive c71 New GM 8.2 415hp . This is a fishing boat and not built for speed .
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The engine is running at its optimum speed. The range is 4600 to 5000. That is likely as fast as it will go. How did you weigh the boat?
  3. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    Provided your numbers are correct, this prop is rather highly loaded, and is working with some cavitation. All fixed structures ( keel, brackets aso) in front of the propeller must be streamlined and smooth. The prop might be a bit happier with some cup added to the trailing edge of the blades.

    In addition, check the tacho calibration and total weight of the boat, it seems something is not quite on spot. Any pictures of the bottom and the shaft supports?
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