When it comes to choosing a boat propeller, you need to understand your boating needs and preferences. The first question you should ask yourself is this: what are you using the boat for? The boat’s propeller determines how it is going to perform, and you’re going to need it to perform differently for different purposes. For example, to optimize your boat’s performance, the propeller you need for fishing may be quite different from the one you need for watersports.
In this guide, we cover the basics of what you need to consider when choosing a boat propeller, including key measurements for the propeller’s size, types of material, and blade count.
Propeller Size: Diameter and Pitch
Propeller size is usually written as diameter” x pitch”. Changing the diameter and pitch will change how your boat performs. Here’s what those numbers mean:
Diameter is the size of the blade. Measure the distance from the center of the hub to the tip of a blade and multiply that by two to get the propeller’s diameter. You can also think of diameter as the length across the circle the propeller makes when it’s in use.
- Larger diameter allows for more power and control but decreases acceleration and creates more drag (e.g. makes it slower). This can benefit larger boats or boats that carry a lot of weight.
- Smaller diameter allows the propeller to rotate faster, which allows for more acceleration. This is typically desirable for smaller boats that travel at faster speeds.
Pitch is how far the propeller will move the boat with one revolution (not accounting for slippage, which will vary from boat to boat).
- A higher pitched propeller makes the boat move faster but decreases acceleration. This is desirable for heavy (commercial) boats.
- A lower pitched propeller has more power and increases acceleration, but makes the boat move slower. This can be ideal for recreational boats.
- Choose a pitch that keeps your boat’s engine within its recommended operating range for best performance.
Materials Used to Make Boat Propellers
There are two main types of materials to choose from for a boat’s propeller, aluminum and stainless steel. In general, aluminum is lighter and more cost-effective, but stainless steel is more durable and offers better performance.
Aluminum is a weaker metal. To compensate for strength, aluminum propellers are thicker, which helps prevent flexing and bending at higher RPMS but causes more drag and reduces the boat’s top speed. However, you can repair aluminum propellers if they get damaged, which makes them a great option for river boats.
2. Stainless Steel
Stainless steel is a stronger metal that offers better performance, but it’s heavier and more expensive. Stainless steel propellers will outlast aluminum propellers, are less likely to be damaged, and offer the best performance, but are expensive to repair or replace if they do get damaged so they’re better suited for offshore boats.
Tip: If your outboard motor is 125HP or less, we suggest choosing an aluminum propeller. A stainless steel propeller will be too heavy, reducing your motor’s performance.
Blade Count for Boat Propellers
The most common blade counts for boat propellers are three or four blades. In general, a 3-blade propeller will offer the most balanced performance, while a 4-blade propeller offers better acceleration and control.
3-blade Boat Propellers
A 3-blade propeller is better for:
- Balanced performance
- Higher top speeds
- Everyday use
…but they offer less control.
4-blade Boat Propellers
A 4-blade propeller is better for:
- Faster acceleration
- Better fuel efficiency
- Heavier, high-performance boats
…but they offer lower top speeds and reduce the motor’s RPM.
Need help choosing a boat propeller? We’re here for you! Contact us with any questions and we’ll be happy to help you figure out which one will best meet your boating needs.