General Rules on Power and Pitch
 

Okay, I need help from the prop masters again....

I guess there is a correlation between prop pitch and horsepower, or is there?

If so what pitch can a pair of 430 hp motors turn?

Or is far more complicated than this?

I am trying t oget into the mid 70's and if I could turn a mega pitch prop it would be easy, but apparently that is not the case.

So what is the correlation between pitch and horsepower? Is there a general rule to follow?

Next is cleaver props, when are they approperate? What do they do differently than others?

Thanks for the education....

Re: General Rules on Power and Pitch
 

the more horsepower you have,the more pitch you can run on any given boat. I had a searay 20 foot boat with a 400 hp 383 and could turn a 21 pitch 4 blade prop at 5300 rpm. I now own a 26 foot boat with a 625 hp engine and can turn a 4 blade 5100 rpm. Many factors in finding right pitch, hull type, boat size/weight, rpm you want to turn your engines at, 3,4,or 5 blade prop, gear ratio in the drive,how high above sea level you boat, fresh or salt water, etc.

Re: General Rules on Power and Pitch
 

There is a correlation between speed and power but there really isn't one for power and pitch.

There are so many factors that pitch doesn't really tell us how fast a boat will go. There are times when we deal with a certain type of boat with a given power, then we can guesstimate a pitch. For the most part pitch doesn't determine the speed.

There are 3 factors that will determine the pitch prop you need to run;

WOT rpm- this is determined by the design of the motor and is typically where the motor makes max horsepower

Drive/transmission gear ratio- these can vary widely and have a large bearing on prop pitch.

Hull- Depending on the hull design and weight this will influence how fast a boat can go.

There are other factors such as the number of blades, drive height, customers goals and design of the prop.

The pitch that is marked on a prop can be several inches off of what the true pitch is.

To determine a starting pitch one would need to know the desired WOT rpm, drive/transmission gear ratio, and length/design/weight of the boat. With this information the proper prop pitch can be determined within a reasonable range.

Matt