# Boat Speed and Prop Slip calculators



## DaleH (Mar 23, 2017)

Here are a boat speed and prop slip calculator if anyone is interested:

Theoretical Hull Speed = ( Prop Pitch X RPM ) / ( LU Gear Ratio X Constant of 1056 )

Prop Slip = ( Theo. Speed - Actual Speed ) / ( Theo. Speed )

I have found the speed one pretty accurate with small open v-hull skiffs. But where a lot of your guys' boats have extensive flooring, decking, and compartments ... I'd expect lower actual speeds due to the actual weight carried. Also note a jon boat will have more wetted surface on the running hull and will be slower.


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## flex (Mar 23, 2017)

Thanks man. I'll try and figure it out. Going to raise the motor up a bit and play with trim this weekend. I just figure I had a fiberglass glasstream bass boat years ago with a 70 that ran 42. This boat weighs half as much it should scoot! Hopefully I can get it dialed. I'll post up as I experiment. Hopefully put a tach on soon as well.

Sent from my HTC One M9 using Tapatalk


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## Crazyboat (Mar 23, 2017)

Knowing ones LU gear ration is key to this.


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## Stumpalump (Jun 4, 2017)

Good calculator here:

https://www.mercuryracing.com/prop-slip-calculator/


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## andrewwty (Dec 21, 2020)

Thanks For the formula. but i don't fully understand how to use it correctly for calculations


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