The choice of a prop affects what performance your boat shall achieve. You shall, therefore, have to think of the prop size, number of blades, material used to make it, its rpm at wide open throttle, and the functions of the boat.
The prop size is a critical consideration. Installing the wrong size could damage the boat and its engine. It shall also mess up its ventilation and cavitation. The prop’s diameter and pitch determine the size. This is normally found on its hub. The first digit you see it the diameter followed by the pitch. Should the boat be powerful enough, the higher pitch would boost its speeds considerably. A larger diameter will mean the boat accelerates much higher.
A prop may have between three to five blades. As the blades increase, so does its performance. Racing boats use three bladed props for their top-end speed. Cupped blades improve on such performance. Cupping refers to the curve at the end of the blade. It shall minimise ventilation and aid the oat in making sharp turns. The rake of the blade is also an important consideration. The angle of the blade with the propeller hub affects the boat’s performance.
You will also have to look at what material was used to make the prop. Aluminum is what is commonly sourced and remains affordable. It is the lighter choice that shall also keep the boat safe when you hit obstacles. It however easily rusts and cannot stand salt water. Stainless steel is, but it comes at a price. It shall last much longer and not be affected by salt water. It shall, however, kill the engine should you encounter obstacles. You need to think of carrying a composite and plastic prop for emergencies.
When it comes to the rpm at the wide open throttle, each engine has specifications unique to it. It shall serve as a guide in your selection.
You will also have to consider what you intend to do with the boat. There exist props designed for different types of boats, like the pontoons, bass boats, as well as those meant for skiing, fishing, racing or leisure. You need to also think of the water on which you shall use the boat. There are always those meant for the lakes, rivers, and other slow waters. There are also designs for the high seas. There shall also be the flat, heavy boats frequently used for transporting passengers and goods. You will also see those meant for high performance such as for racing.
When you are aware of all these factors, it becomes easier for you to choose the right boat prop.