What Is a Boat’s Propeller Pitch?

When it comes to replace your boat’s propeller, you’ll need to understanding the “pitch” and how it impacts the performance of your boat. Unfortunately, most people completely overlook this measurement, focusing more on the material and style of the propeller. Failure to choose a propeller with the appropriate pitch, however, can translate into poor handling on the water.
The size of propeller is defined by two elements: diameter and pitch. The diameter is twice the distance from the center of the propeller to the tip of any blade. Propellers with smaller diameter measurements typically work best on small boats, whereas propellers with large diameter measurements are better suited for large watercraft. You can obtain the diameter measurement of your prop by running a tape measure from the center to a the tip of a blade.

The pitch is a bit more technical than the diameter, so bear with me. Pitch is essentially the distance at which a boat’s propeller would move if it were traveling through a soft solid. Measured in inches, it’s reflective of the prop’s forward movement after completing one full rotation.

Technical jargon aside pitch plays an important role in the boat’s speed and handling. A propeller with a high pitch will result in faster speeds, as the prop travels farther after completing a rotation. With that said, the engine must be able to produce enough power to meet the demands of the propeller. If a high-pitch prop is paired with a low-horsepower engine, the engine may cancel out the speed benefits of the prop.

Lowering the propeller pitch will reduce your boat’s speed, but it will also give you more pulling power (torque) along with faster acceleration. Increasing your pitch, on the other hand, will have the opposite effect by raising your boat’s speed and slowing down its acceleration and torque. Understanding these basic principles will allow you to optimize your boat for ideal performance.

A good rule of thumb to follow when shopping for a new propeller is to assume that every inch of pitch is equal to 200 rpm. In other words, replacing a 24-pitch prop with a 22-pitch prop will yield an average increase of 400 revolutions.

Pitch is only one of the factors you should consider when choosing a new propeller. Also consider the prop’s diameter, material of construction, number of blades (3 or 4-blade models are generally preferred), and brand name.

Tags: pitch, propellers