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Prop Slip Calculator

Prop Slip Calculator

Prop Slip Calculator

What is Prop Slip?

Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. Slip is not a measure of propeller efficiency. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack. If the blade had no angle of attack, there would be no slip; but, of course, there would be no positive and negative pressure created on the blades and, therefore, there would be no thrust.


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1. Enter your GPS verified top speed

2. Enter your drive's gear ratio

3. Enter your maximum achieved RPM

4. Enter the pitch of your current propeller

The Propeller Slip Calculator can be used to calculate two important numbers - Propeller Slip Range and Desired Propeller Pitch.

Reading Your Results

Most setups are in the 5-20% slip range, and of course, every boat is different.

If the percentage is negative, you have input incorrect data, usually, this means the gear ratio is incorrect or the tachometer is not dialed in.

If the percentage shown is greater than 20, there is typically room for improvement by switching to a different propeller, adjusting drive height, etc.

Determining desired Propeller Pitch

When adding power or changing the gear ratio in a given setup, you can calculate how it will affect the pitch of the propeller needed to stay within the desired RPM range.

Simply input the new RPM range or gear ratio, the desired top speed, and what the boat has previously run for a slip percentage, and you will be able to calculate what propeller pitch is needed.

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Talk to our experts

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The Art of Speed



A Mercury Racing propeller is the final critical component of a performance outboard system. Cast from proprietary stainless-steel alloys, hand-finished and zero-balanced by artisan technicians in our prop shop, Mercury Racing propellers offer the ultimate in performance and durability. Choose the precision-tuned performance of a Mercury Racing Pro Finished® model or the race-spec perfection of a Mercury Racing Lab Finished® propeller.


Pro Finish

Step up in performance with a prop that’s hand finished and fine tuned from a raw stainless steel casting with perfectly matching cup heights and a custom blade thickness profile. In most applications a Pro Finish propeller will deliver more RPM and higher top-end speed than a standard production propeller.


Lab Finish

Hand-finished to perfection with additional blade thinning to cut through the water with less power-robbing drag and an increase in top-end RPM. These blueprinted propellers feature perfectly matched blade profiles for consistent multi-engine RPM. The ultimate performance propeller for light-weight boats running over 75 mph.


Mercury Racing® has expanded the pitch range of its popular Revolution® 4 XP propeller line, investing in a new base casting that will be used to produce this high-performance prop in a 15-inch diameter and pitches of 26.0, 26.5, 27.0 and 27.5 inches. This new casting will be used to replace the current 14.63-inch diameter Revolution 4 XP at 26.0- and 26.5-inch pitch sizes. 


The MAX5 propeller is designed for single- and multiple-engine applications, including the 400R outboard and the 600 SCi sterndrive.


We recently executed a propeller test on a new Lund 208 Tyee GL powered by a V8 Mercury Pro XS 300 outboard with the Mercury Racing Bravo I® FS propeller...

An image with a man smiling will driving a boat with a black and red Mercury Racing 300R outboard with water in the background.