You should settle for the right boat prop when you need your boat to work properly. 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. By choosing the wrong size, you shall inflict damage on the boat and the engine. It shall also mess up its ventilation and cavitation. The size is dependent on the prop’s diameter and pitch. These are normally stamped on its hub. The first digit you see it the diameter followed by the pitch. With a powerful enough boat, a higher pitch shall boost the speeds travelled. A larger diameter enables the boat to reach higher acceleration.
A prop can come with three to five blades. The more the number of blades, the better its performance. For higher top end speed, racing boats will need three bladed props. Cupped blades are even more preferred. Cupping refers to the curve at the end of the blade. It is what prevents ventilation and helps the boat make 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 lightweight, and is guaranteed to protect the boat should you hit obstacles. It however easily rusts and cannot stand salt water. You would need stainless steel for that, but be prepared to pay its higher price. It shall last much longer and not be affected by salt water. It will, however, cause damage to the engine in case you hit an obstacle. You shall need to have a composite and plastic prop for emergency cases.
As for the rpm at the wide open throttle, there is a specification for each engine. It shall serve as a guide in your selection.
You need to also think of the job the boat was designed to do. There are props designed for different types of boats, such as pontoons, bass boats, as well as those meant for skiing, fishing, racing or leisure. You should then think of the water where the boat shall travel. Some of these props are meant for the lakes, rivers, and other slow waters. There are also designs for the high seas. You will find some for flat, heavy boats commonly used for transporting passengers and goods. You will also see those meant for high performance such as for racing.
These are the factors that shall help you pick the right boat prop.