The most frequently asked question we are asked about outboard and stern drive boat propellers is: What boat propeller should I be using on my boat?
There are two reasons why people call us about getting a propeller for their boat. Customers either need a replacement boat prop for the one they have because they have damaged or lost their boat propeller, or they are not happy with the performance of the boat propeller they are using now and want to see if there is a better boat prop they can buy. Basically people ask us the same general question about boat propellers, and this is the one we get all the time and the answer we give.
Finding what boat propeller you should be using on your boat is relatively simple to determine. But a little hard to explain. There is a kind of formula you follow and here it is.
First you find out what your engines wide open throttle ( W.O.T.) operating RPM range is, which is the range your engine is making the most horsepower and is the safe range to run your boat at full speed. Look in your engine owners manual for this or if you don’t have a manual you can look it up on-line.This is the RPM range you should be obtaining with just you in the boat driving at full speed and trimmed up if you have trim. The operating RPM range you should be in is generally a range of 400 up to 1000 RPM’s. depending on what engine you have.With just you in the boat and the right pitch boat prop, you should be in top half of this RPM range. This is where your engine is creating the most horsepower which is always rated at full speed. If you are not there then you need to change what pitch prop you are using. Boat propellers work like gears in a car. Too low of a gear or pitch you get too many RPM’s at full speed. Too high of a gear or pitch you don’t get enough RPM’s at full speed. Either way you are not getting the best performance you should be getting like if you had the right gear or pitch.size. Concerning propeller pitch size please see our article on that subject.