When you see how boat propellers are described in terms of size it is done with actually showing two sizes for one boat prop. Example: 14 1/5 x 19. The first number is the diameter of the propeller measured from the center of the prop shaft hole of the prop where the prop shaft goes into out to one blade tip then doubled. If you measured seven and one quarter inches on your prop then the diameter of your prop is 14 1/2 inches. Simple.
How you measure the pitch of a boat propeller is a little more complicated. How do you measure the performance of a boat propeller when it is used in a liquid?
The answer is you really can’t. Boat propeller makers then determined that the best way to measure performance was not do it using water because that could be nearly impossible but to see how the prop motion would react going thru a solid. The pitch is how far a boat prop will travel thru a solid one revolution theoretically, measured in terms of inches. A 19 pitch prop should go 19 inches forward one turn. In water how to see the amount of slippage that is happening because the prop can’t get a good grip on water would be extremely hard to measure. The degree of slippage is much easier see and to improve on using the solid model. Using a solid as a model is also much more accurate when designing and making boat propellers that will work the best. You need a variety of prop pitches that work differently from each other because just one pitch size is not going to work for every size boat and motor combination. The degree of slippage is much easier to improve on using the solid model.
For the best performing boat propellers at the best prices check out our website or call us at 1-800-573-5533