Re: Prop Question
This response may be a bit late but here it is. There are many variables to consider if you are contemplating any changes to a propeller for the sake of modifying an engine's (boat's performance). See below
How a Propeller Works: (Runquist propellers.com)
The propeller is the final link in a boat's power train. Its job is to take the torque created by a marine engine and convert this torque to thrust. A propeller is designed to control the engine's RPM and hold it at wide open throttle to the recommended RPM range specified by the manufacturer of a motor. This preferably should meet the crest of the power curve of the motor.
The power curve is the RPM range where the motor is developing its maximum horsepower and efficiently. If the motor revs beyond this point, it is over revving, and if the motor is not able to reach this point it is loaded down. Either way, this causes poor performance and unnecessary wear and strain of the drive train.
Propeller Pitch, Rake and Diameter (cupping also) all play a major role in determining the outcome. If you search around on the web there is a site that will help you with all the necessary theoretical calculations to select the propeller you want or simply restore the correct prop to your engine/boat.
You will need to supply some of the information for the formulas to work though.
