Marine Propeller Calculator

This calculator requires the use of Javascript enabled and capable browsers. This calculator is designed to give any missing value from the 5 variables needed for marine propeller calculations. They are engine RPM, prop gear ratio (normally for 1.5 to 3.0), prop pitch (the distance that a propeller would move forward in one revolution), prop slip (the efficiency of the prop, lower at high speed, but perhaps very inefficient at low speed) and the boat speed in mph. Enter any 4 variables and the 5th variable will be calculated. Our defaults are set up so that boat speed is the missing variable; however, you may clear any of our defaults and insert your own values.

As our graphic shows, a propeller is identified as for instance, 13 3/4 x 21, if it has a blade diameter 13 3/4 inches with a pitch of 21 inches, the amount of forward travel in one revolution. The table below generally defines the terms.

Enter Any 4 Values
Engine RPM RPM
Prop Gear Ratio X:1
Propeller Pitch Inches/Rev
Propeller Slip .XX
Boat Speed MPH
Terms Used
Units Definition
Engine RPM Engine Revolutions Per Minute
Prop Pitch Inches Per Revolution (cupped props +1)
Prop Slip Decimal Or Integer (example .30 or 30)
Boat Speed Measured Miles Per Hour
Updated 8.12.11

Leave us a question or comment on Facebook
Search or Browse Our Site
Free Information Calculators and Converters

International Copyright Violation
Registered® Trademark™ and Copyright© 1973 - CSG, Computer Support Group, Inc. and CSGNetwork.Com All Rights Reserved