Propeller Basics
Propeller fundamentals are one of the most important aspects of boat performance yet not very many people truly understand how the propeller itself actually effects this. We commonly here customers asking if they can just install a bigger propeller to get more speed out of their boat. Here are just a few things to consider;
3 Blades vs. 4 Blades
In general the 3 blade propeller offer more speed while the 4 blade offers better thrust and acceleration. Today with the engines producing even more torque, we are starting to see more of the 5 blade products. In general the higher number of blades on a propeller, the lower speed the boat will be able to stay on plane.
Diameter
The diameter is the distance/circle that a propeller makes when rotating.
Pitch
The pitch is the theoretical horizontal distance in inches that the propeller travels when rotated. For example a 23p propeller will travel 23 inches in one revolution (not factoring in slippage).
Rake
Is the angle the blades are tilted towards the rear when measured looking at the side of a propeller. This allows using a larger propeller (more blade area) within the same diameter. Positive rake generally benefits in acceleration and good bow lift.
Cupping
Cupping is a means of simulating addition pitch by "bending" the trailing edges of the propellers to increase the "grip" of the propeller in the water. This feature reduces slippage and is usually used with larger, more powerful engines.
IMPORTANT LINKS
– Propeller Fundamentals