The Proper Props

The numbers and letters associated with a boat’s propeller designation often don’t mean much to boat owners. When we are talking about propellers, a 15½ × 17 is NOT a multiplication problem! These numbers convey the propeller’s suitability in delivering reliable and efficient performance. Using the right propeller can ensure that your boat is as much as 30% more fuel efficient. Check our website performance reports found in View Performance Data for each model to see what we test, use and recommend for new Grady-Whites. Your dealer can help with your needs for older Gradys.

The basic propeller designation is straightforward. For a 15½ × 17, the first number refers to the prop diameter, or the distance across the circle made by the propeller blades when rotating. The second number in the description refers to the propeller pitch, or the ideal distance in inches the boat moves with a single revolution of the propeller, e.g. 17 inches. The lower the pitch, the lower the “gear,” meaning you get on plane quickly with a low pitch, but at some penalty on the top-end speeds. Also, the smaller the diameter, the higher the pitch can be for a given boat/motor combination. With the larger four-stroke V6 and V8 engines or inline 4-cylinder engines used on Grady-White boats, we can power higher diameter props to achieve the desired level of efficiency and performance. A great deal of testing goes into the props that we recommend and install, and your dealer is a great source of knowledge about the right kinds of props for you. See our Customer Tips area for more tips for boat handling & seamanship.

Other letters you may notice in the propeller technical description like “M” and “SS” and “SSII” refer to Yamaha’s propellers series designation. However, an SDS (Shift Dampening System) designation refers to the prop hub, indicating a kind of shock absorber mounted on the shaft that ensures a smooth, even shifting into gear, as well as making it easy to interchange various propellers.

Even the rugged and durable stainless steel propellers we use on every new Grady-White will get nicked and dinged from normal use and should be inspected regularly to avoid vibration, noise, and lesser fuel economy and performance. Performance can be reduced by ten percent or more depending on the damage. A professional prop shop can recondition most minor damage. See your dealer if you experience more serious damage.