The Right Propeller

Changing out your props? Here are five things to know first, straight from the experts.

- Alan Jones

Selecting the right propeller is part guesswork and part science. To home in the science side, we asked three of the top experts in the marine industry for their best tips on choosing the right prop for your boat-and-motor combination.

Our panel included Gary T. Diehl (GD), Mercury Marine's senior category manager for props and gauges; David Meeler (DM), Yamaha Marine's product introduction and information manager; and David Greenwood (DG), Suzuki Marine's general manager for the Marine Technical Center USA. Here is what they had to say.

DIALING IN PITCH AND DIAMETER

DM: Each inch of the pitch will affect engine speed by 150 to 200 rpm. As the pitch goes up, rpm goes down. When the diameter goes down, rpm rises. Each one-quarter inch in diameter has the same effect. A boat should be propped to where it's properly trimmed out and the wide-open throttle (WOT) rpm is in the top 30 percent of the manufacturer's acceptable WOT rpm range with the average load in the boat.

Prop selection is more than pitch and diameter. Blade shape, geometry and rake also affect performance. Many times, a better solution is available based on these factors than just changing the pitch, diameter or the number of blades. Talking with a propeller professional can help.

DG: When trying to improve the hole shot on heavier hulls, I like to reduce or increase the diameter first and then do the opposite with the pitch.

GD: Most manufacturers have prop models for specific applications, and this is a good place to start the dialing-in process. Usually with these, the diameter is the same, so you only have to select the correct pitch to match your needs.

WHEN TO CHOOSE AN ALUMINUM PROP