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Thread: Formula

  1. #1
    LUVNLIFE
    Hey can I get the formula for calculating mph, horspower, propsize,rpm with slip deal. Thanks in advance guys. Cale

  2. #2
    bigkatboat
    I can tell you about the prop speed +- slip equation. Engine RPM divided (or multiplied) by gear ratio. Times prop pitch, divided by 12". That number times 60, divided by 5280 = prop speed +- slip. I/O's example; 5000 RPMs, divided by 1.50 = 3333.33... 3333.33 X 24 (pitch) = 79999.99. 79999.9 divided by 12" = 6666.6 6666.6 X 60 = 399999.9 . 399999.9 divided by 5280 = 75.757 (prop speed) Example 75.757 X .90 = 68.18 MPH (good boat speed @ 10% slip) V- drive (overdriven boats) can have many variables as to top speed. (wet VS flying) 6500 RPMs, X 1.29 (gear ratio) = 8385. 8385 X 16 (pitch) = 134160. 134160. divided by 12" = 11180. 11180 X 60 = 670800. 670800 divided by 5280 = 127.045 (prop speed) 127.045 X .80 = 101.636 MPH How fast do you really go?

  3. #3
    Tahiti350
    Try this link: http://www.admboatworks.com/pitch.htm
    They have a cool calculator right on the website. Haven't GPS'd mine yet, but believe it accurate, as long as your slip percentage is close.

  4. #4
    LUVNLIFE
    Thanks for the info guys. Cale

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