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Propeller Calc

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Propeller slip calculator for powerboats

Please use this calculator to figure out all parameters in regard to pitch, gear ratio, RPM, speed and slip. Enter any four variables, and it will calculate the fifth. The calculated field will be highlighted.

Pitch is the theoretical forward movement for one complete turn of the propeller. Every centimeter of the boat that is in contact with the water induces drag. Therefore the distance traveled is not the same, since the propeller is "slipping" behind the theoretical distance it should travel with each rotation. The difference between theory and reality is called slip.

Depending on your application, slip will typically range between 5% and 30%. A lower number is not always what you are after. Slip of a prop changes with operating conditions, and is not a direct measure of efficiency. Please consult professionals for guidance.

Best regards from the Norwegian offshore powerboat team J-20. Happy powerboating!