The correct prop for your boat will make your engine turn within it's maximum rated RPM range at full throttle
1) What is the maximum RPM you are able to achieve now? (provided by your tachometer)
2) What is the maximum RPM range of your motor? (provided by your owners manual or dealer)
3) What size and model propeller you are currently running? (provided by numbers stamped into propeller)
Many boaters complain that this is not relevant, since they never run their engines at full throttle.
But the engine manufacturer has designed the engine to achieve it's maximum power, efficiency and longevity when propped to achieve it's maximum RPM. Ignoring this rule risks damaging your engine.
If your current prop runs within that range, then it's a candidate for being the correct propeller. (more on that later) If the RPM is too low, you need to decrease the loading caused by the propeller, usually by reducing the pitch. If the RPM is too high, then a pitch increase is in order. The change in RPM caused by a one-inch pitch change varies by application, but it's usually 150-250 RPM for most outboards and stern drives.
Most engines have a maximum RPM range of, let's say 5,000-5,500. A prop that turns 5,000 RPM will offer a better cruise speed and efficiency, while a lower pitch propeller that turns 5,500 RPM will provide a better hole shot. Both are potentially the correct propellers. The correct propeller for you is the one that matches how you use your boat. A heavy water skier will likely want the lower pitch, while a cruiser will go for the higher pitch.
There are many propellers that will turn the right RPM on your boat. A simple example is aluminum versus stainless steel on an outboard or a stern drive.The same size aluminum and stainless propeller may turn about the same RPM, but the stainless prop will be faster, provide a better hole shot and bite better in turns. A four blade prop, sized to run at the same RPM, will provide an even better hole shot, plane at lower speed but run slower at top end. The right prop for you will depend on how you use your boat and how much money you want to spend.
We will work with you, and help you find the correct propeller. All you need to do is be able to answer the three questions above. If you can answer the three questions above, and we make a recommendation to you, you can buy the prop, *try it out, and *return it if it's not the right one. You'll need to know the answers to the three questions again, because the answers will have changed.
*try it out = put it on the boat and run it, you'll know in 5 minutes if it's the correct one. "try it out" DOES NOT MEAN run it for the day or the weekend and then make a decision.
*return it = exchange it for the correct one, as long as it the same condition as it was when it left here, and with the correct box. Don't use it to open up any oysters, they make special knives for that.