The size is usually indicated on outside of the propeller hub. It is usually written like this (examples):
The first number is the diameter (11.25) and the second number is the pitch (13).
Some brands use a different way to indicate the size or model.
Yamaha adds a letter to indicate the type of blade design. Mercury Mercruiser uses a number code ending with pitch size (in this case it is pitch 21). Solas propellers use the last 4 numbers to indicate size (in the example above diameter 9.3 and pitch 10). Volvo Penta uses a separate number system, see here for an overview table.
If you have lost your propeller in the water or it has become unreadable, please contact us for advise.
The pitch of your propeller is the most important property. It is the “curvature” of the propeller blades. The pitch (e.g. 13) represents the forward distance (number of inches) which a propeller would make in a complete rotation.
A larger pitch means more curvature and potentially a higher top speed. A smaller pitch means less curvature and thus more acceleration.
Think of pitch as the gear of your car. Starting in the first gear (small pitch) you can accelerate quickly, but your top speed is limited. Driving away in a higher gear (larger pitch) is slower, but your top speed will be higher. However, if you have a too large gear (pitch) the engine will not be able to reach enough RPM (rotations per minute) and will thus also not be able to come up to speed. With a too small gear (small pitch) the engine will make too much RPM which limits your speed and may also damage your engine. Continue reading below to find out how you can get a good indication of the pitch you should choose.
If you are currently satisfied with the performance of your engine, we recommend to choose the same pitch. However, if you wish to change the performance you can consider a different pitch. For example if your engine currently makes too much or too few RPM (rotations per minute), or if you want to use your boat for a specific purpose (eg. waterskiing).
A good indicator for selecting the optimal pitch is the RPM your engine makes at ´wide open throttle´ (WOT). Each engine has a prescribed ´optimal´ RPM that it should be making at wide open throttle. This differs per engine but often it is between 4500 and 6000. You can check your manual, or check this RPM Range Chart for the most common engines.
If currently your RPM is too high, you may consider a larger pitch that will improve your top speed. If the RPM is too low, the engine is not reaching its full potential because of a too large pitch. In this case choosing a smaller pitch can result in better acceleration (because of the smaller pitch) and higher top speed (now the engine can reach full RPM).
If you’re changing pitch on a recreational boat, remember that each inch of pitch translates to a difference of approximately 200 to 300 rpm. Lowering the pitch will increase rpm and choosing a larger pitch will reduce the rpm. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 to 600. For smaller horsepower engines (up to 30 hp) this difference is usually bigger: one pitch can already make such a difference.
Most propellers have 3 blades. For speed this is the most efficient design. For extra thrust at low speeds you may consider a 4 blade design. This will give more acceleration but will go at the cost of top speed. This is useful in situations such as waterskiing, wakeboarding, or when accelerating a relatively heavy boat.
Stainless steel propellers are stronger than aluminum propellers. This makes them less vulnerable to scratches by sand. Because of the stronger metal the blades are usually thinner which improves the efficiency of the propeller. Stainless steel is relatively more expensive than aluminum propellers.
The diameter is the length of your propeller from left to right (see picture). The propeller diameter that you can choose is determined by the shape of your engine. If you select your engine on our website you will automatically find propellers that have a diameter that fits on your engine. Please note that choosing a 1 inch larger diameter has approximately the same effect as a 2 inch larger pitch.
The hub system is the connection between the propeller and the propeller shaft of your engine. All propellers that we deliver are standard including a hub. Most of them have a rubber pressed-in hub. Some propellers have an exchangeable hubkit (especially models with higher horsepower).
The propeller is fixed on the propeller shaft with mounting parts. A nut kit usually includes a nut, cotter pin, washer and spacer. Normally you only need to replace your propeller and can re-use these parts. In case your propeller is lost while sailing you may have lost these parts as well. The right nut kit is suggested at the product page of the propeller for your engine.
A new propeller will only fit if the number of ´tooth splines´ on your propeller shaft is the same as the number of tooth splines on the inside of your propeller hub. When selecting your engine in our shop, it will automatically select the propellers with the right number of tooth splines. To verify if your new propeller will fit, you can check the number of tooth splines as mentioned on the product page.