Understanding Propeller Slip
Slip is the difference between theoretical and actual speed. Learn how to calculate it and what your numbers mean.
What is Propeller Slip?
Propellers act like screws, but water isn't solid wood—it's fluid. "Slip" is the lost distance per revolution caused by the fluid yielding.
Low Slip (5-10%): Efficient, but check if you are over-propped (engine lugging).
High Slip (>20%): Inefficient. You are burning fuel to make bubbles (cavitation/ventilation).
The Formula
Slip % = [(Theoretical Speed - Actual Speed) / Theoretical Speed] * 100
Use our Interactive Slip Calculator to check your numbers.
Prop Slip Calculator
Calculated Slip--%