BAY PROPELLER INC.

* DIAMETER : This is the distance across the circle made by the blade tips as the propeller rotates, another way to measure Diameter would be to measure from the center of the propeller to the tip of one of the blades and multiply by 2.

* PITCH : This is the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw in wood. A propeller identified as a 14 x 19, has a 14 diameter ( 7" from center to tip, multiplied by 2 ), with a 19 pitch. Theoretically, this propeller would move forward 19" in one revolution. There are two types of pitch, constant pitch and progressive pitch.

Constant Pitch means the pitch is the same at all points from the leading edge to the trailing edge.

Progressive Pitch starts low at the leading edge and progressively increases to the trailing edge. The pitch number assigned is the average pitch over the entire blade.

* CAVITATION : Cavitation is the phenomena of water vaporizing or boiling due to the extreme reduction of pressure on the back of the propeller blade. Cavitation can be caused by nicks in the leading edge, bent blades, too much cup, sharp leading edge corners, or incorrect matching of propeller style to the boat and motor.

* VENTILATION : Air from the water surface or exhaust gases being drawn into the propeller blades which causes the propeller to over rev and losing its thrust. Ventilation can be caused by the motor being mounted too high or by over trimming.