Shape and size

Propellers come in a wide variety of shapes and sizes. Those sizes are referred to as diameter and pitch. The first and most important decision when picking a propeller is to match the propeller pitch to the engine manufacturers recommended WOT (wide open throttle) range. This means it is important to be able to turn the minimum rpm the engine was designed for with the throttle fully advanced. As a propellers pitch rises, it creates a larger weight or restriction for the engine to spool up to higher rpm’s. A 50 HP engine may only be able to turn a 15-pitch propeller where as a 750 HP  offshore race engine may be able to turn 30 plus inches of pitch. Once the correct pitch is determined, the plot thickens…