The thinner the blade's edges, the less energy required to spin it. They can also provide more bow lift for added speed. In recent years, 4- and 5-blade props have become popular because they suppress vibration and improve acceleration by putting more blade area in the water, especially when the prop is breaking the surface. Cup is a lip or sharp contour near the trailing edge of the blade that keeps water on the blade longer for high-speed applications. A perpendicular blade has no rake, whereas a high-performance blade may have 20 or more degrees of slant aft to decrease blade drag through the water. Blade rake describes the angle of the blade to the hub. Two other considerations, blade rake and cup, also affect your propeller performance. Some boaters don't like the variable-pitch because it's more expensive and just as vulnerable to damage, while others say their high initial cost can be balanced against the cost of carrying a second prop for different activities. A variable-pitch propeller allows your boat to shift gears like a car, since it's designed to maintain a low pitch angle during initial acceleration, then shift to a higher pitch angle in the higher rpm ranges. While progressive pitch gives you some compromise in the tradeoff between acceleration and top end, it's still a fixed blade. The number designated on a progressive-pitch prop represents the average pitch. The water's surface, progressive-pitch props are used in virtually all outboard applications. Built for high-speed and high-rpm applications, including those instances when the prop is breaking On a constant-pitch prop, the pitch stays the same across the face of the blade, while on a progressive-pitch screw it starts low and increases across the face of the blade, making the prop appear twisted. Just to make things a bit more confusing, there are two types of pitch: constant and progressive. Assuming you use the same engine and boat for three different sports, a 13 x 21 prop might be ideal for general cruising, while a 13 x 23 would be more suitable for lightly loaded fishing trips, with a 13 x 19 just right for waterskiing. The same horsepower motor on a lighter boat needs a higher pitched prop to give it more speed and efficiency in its use of the engine rpm. Generally, the heavier the boat, the lower the prop pitch required. That calls for a careful match between engine power, gross weight and the intended use of the boat. You'll get optimum performance when pitch and diameter allow your motor to operate within the factory-recommended full-throttle rpm range. Pitch is the number of inches your boat and motor should move forward in the water when that prop makes one complete revolution. Diameter is the width of a circular column of water flowing off the face of the prop. Props are initially classified by numbers showing diameter and pitch. But PM wanted to go beyond theory and show how different props can change boat performance, so we tested six props (on a single boat) that incorporate a variety of materials and designs, from the most basic to the technologically advanced. Whether you're interested in props with names like 'chopper' or 'cleaver,' or if you just want to know the differences between sizes, materials and trade names, your dealer's an expert. Besides, having more than one prop on board is cheap insurance and good common sense. Choosing a prop with the correct pitch, diameter, rake, surface area and contour will keep your engine within factory-recommended wide-open throttle (WOT) rpm ratings. Fishing, cruising and waterskiing all place special demands and different loads on your engine. Regardless of your rig's size, horsepower or application, the right prop can make the difference, whether you seek increased speed, better handling or more power.Д®ven if you're happy with your boat's performance, you and your family might participate in more than one watersport, and you may benefit from changing props. Yet the easiest and least expensive way to improve performance is to change propellers. Each year, hundreds of boaters spend countless thousands of dollars on machine-shop equipment and bolt-on gadgets in their quest to increase outboard horsepower.

Quicksilver prop numbers