The table below generally defines the terms. 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.Īs 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. Enter any 4 variables and the 5th variable will be calculated. 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. This calculator is designed to give any missing value from the 5 variables needed for marine propeller calculations. This calculator requires the use of Javascript enabled and capable browsers. Marine Propeller Calculator Marine Propeller Calculator
