What effect does prop diameter have on a boats performance when speaking in the 14"-15" range. Does 1/4" or 1/2" make a big difference when staying with the same pitch?

Diameter can make a difference in the performance of a prop. As to what effect it will have on your boat depends on many variables, such as;
Drive/ motor height
type of boat
weight of boat
type of performance desired
etc.

Your paticular boat may respond differently to diameter changes than another boat.

The only way to determine what is best for your boat is to test different props and see which one gets the results you are looking for.

As a general rule the diameter has to do with the blade surface area. The greater the blade surface area the greater the thrust of the prop. This is one reason a four blade prop gets the boat out of the hole better than a three blade prop.

A 1/4 or a 1/2" change could make a difference on your boat. The only way to find out for sure is to test and find out.

Matt
Throttle Up Propellers
www.throttle-up.com
[email protected]

DIAMENTER BIGGER OR SMALLER WILL CHANGE THE RPM. The rule of thumb is that per1/4" will change the rpm 250

are the pitch,and the dia,needs to be measured from center of hub to the tip of the blade and double it,this will give you the correct size or look up the numbers all merc props start with a48- and all omc props are a six digit number such as 382764 is a omc 131/4x17 pitch.

What about 1" of pitch?

1" in pitch will change rpm 150-200rpm.

BT

The last prop, I changed from a 25 mirage plus to a23 pitch mirage plus and then labbed the prop HAMMERDOWN GAINED 500 RPM right what he wanted and needed and picked up 2 mph he also reported out of the hole was alot quicker and mid range was alot quicker response/ it just really depends on what the customer needs but there are limits.