What You Need to Know About Propellers

Propellers are described in numbers. The first number is the propellers diameter and the second number is the blade pitch.

Propeller Diamter 101

If you draw a circle around propeller blades, this will give you a diameter in inches.

Pitch is the theoretical distance that a propeller moves your boat forward in one rotation. Again this number is in inches.

This means that a 14 x 19 propeller has a diameter of 14 inches with a pitch of 19 inches. In conversation, most people would describe this simply as a 19.


  • Generically, every inch of pitch is worth 150 - 200 RPM
  • Increase pitch an inch and the full throttle RPM should drop around 150-200RPM
  • Decrease pitch by an inch and the RPM should increase by roughly 150-200RPM at full throttle


Too few RPM at full throttle might mean you need less pitch. Too many RPM at full throttle, you may benefit from a propeller with more pitch.