You need to pick the right boat prop if you expect your boat to perform at its best. This means you need to pay special attention to the prop size, number of blades, the material used to make it, its rpm at wide open throttle, and the functions of the boat.
The size of the prop is an important factor. If you get the wrong size, you shall damage the boat and its engine. It shall also mess up its ventilation and cavitation. You will know what size you need by looking at the prop’s diameter and pitch. These are normally stamped on its hub. The first digit is for the diameter while the second one is for the pitch. When the boat is powerful enough, a higher pitch will boost the speeds travelled. A larger diameter enables the boat to reach higher acceleration.
You will see a prop with between three to five blades. A prop with more blades tends to perform better. Racing boats use three bladed props for their top-end speed. Cupped blades are even more preferred. Cupping is the curve at the end of a 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.
The material for making the prop of the boat shall also matter. Aluminum is what is commonly sourced and remains affordable. It is lightweight, but will keep the boat safe in cases of obstacles. It however easily rusts and cannot stand salt water. Stainless steel would, but you would then have to pay a lot more for it. 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. This should guide you as you make your choices.
You need to also think of the job the boat was designed to do. 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 should then think of the water where the boat shall travel. There are always those 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. There are some meant for high performance like racing.
Once you figure out such details, choosing a prop becomes much easier.