Re: quick question?
If you are changing from a 15 inch diameter prop to a 19 for example, there would indeed be a change in rpm. However, a 19 inch prop does not belong on an engine designed to run a 15 inch prop and besides, it would not fit. It has to do with blade area. Much more blade area on a 19 inch prop than a 15. If you are comparing pitch differences within a given prop type (say 15P, 17P, 19P) the diameter will decrease slightly as pitch goes up, and increase slightly as pitch goes down. Those changes however generally amount to about 3/4 inch which means nothing other than it is part of the prop design for that particular series of engines.
