Boaters understand the right propeller will allow them to get more from their boat.
When this prop is matched to the application, the engine power is maximized, and acceleration and handling improve. What should an owner consider when purchasing a propeller to ensure they select the right one?
How Do Propellers Work?
Propellers feature a hub surrounded by symmetrical blades. The blades are twisted to push water toward the rear during turns, propelling the boat forward. Most blades on an aluminum high performance propeller or any propeller turn clockwise.
However, some boats have dual propellers, one rotating in a clockwise direction and a second rotating in a counterclockwise direction, for stability and improved steering.
Propeller Design
Props come with two numbers that indicate the diameter and pitch.
The diameter is determined by the blade’s overall size measured from the tip. Larger diameters move more water and provide more power. The propeller manufacturer determines the diameter, so boat owners should focus on the pitch.
Pitch refers to the distance the boat travels with each propeller revolution. Low-pitch propellers provide more power, but the boat moves slower. High-pitch propellers allow the boat to cover more distance with each revolution, so it travels faster.
Select a pitch that maintains the recommended engine RPM for optimal performance.
Rake should also be considered when buying a propeller. This term refers to the angle between the blade and the hub. Some are flat, while others are progressive, and the maximum rake is 20 degrees.
High-speed lightweight boats benefit from a high-rake propeller, which will lift the bow out of the water higher. Excessive rake can reduce the boat’s overall performance while straining the engine.
Cupped propellers feature a lip on each blade’s edge, which creates additional space between the blades to decrease slippage and ventilation. Cups on the blade tips increase the rake angle and accompanying bow lift.
Cups on the trailing edge offer more power but slow the engine.
The number of blades impacts the efficiency of the propeller. Fewer blades mean more efficiency but also more vibration. Most boaters choose a three-blade propeller for optimal performance, efficiency, and speed.
Increase the number of blades and see an increase in acceleration and decrease in ventilation. Four-blade propellers are ideal for high-performance applications, and five-blade models are used for tow sports and when the boat often travels in rough waters.
Aluminum props provide the right balance between performance, durability, and cost. Stainless steel models are significantly stronger, last longer, and perform better. Acceleration improves with a stainless steel propeller.
Choosing a Propeller
When choosing a propeller, consider how the boat is typically used.
Owners might find they need to switch props based on different applications. To offer the highest horsepower, the prop should keep the engine RPM at the midpoint or higher of the wide-open throttle under a normal load.
Look at the engine’s propeller guide to determine the correct pitch, number of blades, and material.
Perform a water test to ensure the propeller suits the boat and application.
Consider investing in a spare prop, as boaters can never know what will happen when they are out on the open water. This propeller doesn’t need to be the same as the one commonly used. A spare is great for emergencies and allows an owner to get more out of their boat.