How to Choose a Boat Propeller

birdseye view of a boat on the water

Knowing how to choose a boat propeller really comes down to knowing whether or not you want a lot of speed, or more power to transport a boatload of people over the lake comfortably and easily. This can only be accomplished through trial and error, research and visiting several boating outlets. It may even entail asking for an individual demonstration. Keep in mind that you might have to purchase more than a single propeller because there are different varieties that will be able to give you either top speed or good handling, but you won’t be able to get both of these with just one propeller.

Propeller Dimensions

Two of the most important things to understand in choosing a propeller for your needs is to know both the pitch and diameter of the propeller in inches. This is an important factor in choosing the correct propeller because these dimensions are the actual size of the propeller. Another, equally important consideration would be the material from which your propeller is made. Propellers can be constructed of aluminum, stainless and polished steel, or a very heavy plastic composition. Each of these has a price tag, with plastic being the least expensive and polished stainless steel being the most expensive. Another very important consideration in choosing propellers is that each will have a varying effect on your boat’s engine. What you are striving for is to allow your engine to operate at the manufacturer’s maximum recommended engine RPM at full-throttle as this will allow your engine to run more smoothly.

Sizes of Propellers

There are a number of different ways to find out what is your engine’s recommended propeller diameter and pitch. The first place is in your engine’s owner manual. Alternatively, you can do research utilizing a propeller information chart for your specific engine. Lastly, look inside your existing propeller hub for a stamped serial number. A propeller’s diameter is considered the distance across the propeller’s hub, from the outer edge of the propeller’s blades. Pitch of a propeller can be measured as the approximate distance your boat will move forward for each of the revolutions of the blade. A good example of this would be that a 14”x 21” propeller will have a 14-inch diameter, with a 21-inch blade pitch.

Why Size Matters

A propeller with a high pitch will move your boat faster at your engine’s maximum RPM, but it will slow down your acceleration, or the time it takes to reach your highest speed. Conversely, if you choose a propeller with a low pitch, it might help you to develop more power and acceleration, but it will lower your overall top speed. The last consideration is not to choose a propeller that is either too big in diameter or too high in pitch because this will prevent your engine from getting up to its maximum recommended RPM. This can cause poor performance and will strain your engine. In the long run, too much strain on your engine will destroy it and you will have to replace it.