There are many different types and styles of propellers, and there is no specific propeller for all boat types. The General Rule is that the propeller can help your boat's engine reach the upper portion of the WOT ( Wide Open Throttle) range, which the manufacturer specifies, without exceeding it. For example, if your outboard shows WOT is 5000-6000 rpm, you would need a prop that allows your engine to turn between 5700- 6000 RPM with your average to heavy load on the boat. Check for fuel, full bait, live wells, batteries, and passengers.
Below are steps to choose the right propeller
- Choose the boat most similar to yours and note which propeller is listed
- Check the prop solutions that are workable for your particular horsepower
- Look for the same series name, decide the best pitch for you, and adjust it based on weight and altitude (heavier weight or altitude pitch down, and light or low means pitch even or slightly up.)
One Inch of Propeller Pitch = 150- 200 rpms
What Does the Yamaha Propeller Series Mean?
| Propeller Mark | Model | Gear Case Diameter | Spline Count |
| A | 2 | 1.75" | Shear Pin No Spline |
| BS | F2.5 | 2.00" | 9 |
| B | 4,5 | 2.00" | 9 |
| BA | 4,5,F4,F4A, F6A | 2.00" | 9 |
| N | 6, 8, F6, F8 | 2.25" | 7 |
| R | T8, T9.9 | 2.50" | 8 |
| J | 9.9~F20 | 2.50" | 8 |
| F | 20~30, F25 | 3.00" | 10 |
| G | 40~55, T25~ F60 | 3.50" | 13 |
| K, KL | 60~130,T50~F115 | 4.25" | 15 |
| M/T,ML/TL | 150~300,F150~F300 (4.2L V6) | 4.75" | 15 |
| X,XL | F300/F350 TR (V8) | 5.25" | 17 |
| Y | F425,F450 | 6.00" | 18 |
Propeller Terminology
Pitch
The distance (measured in inches) that a specific prop could go in a single full revolution if it passed through a solid. Although the top speed will be lower, the hole shot and "pushing power" will be better with a lower pitch. A prop with a steeper pitch will accelerate less yet perform better at higher top speeds. The correct prop will allow your engine to achieve the upper part of the WOT range specified by your manufacturer with a normal to heavy load. (without exceeding it) Each inch of pitch is equal to about 150+/-50 RPM
Diameter
The width of the "circle" created by the blade tips during rotation. A larger diameter, for example, moves more water and reaches deeper (which is especially advantageous for larger or heavier boats). Conversely, a smaller diameter is typically preferred for lighter boats, as it allows the propeller to operate at a shallower depth.
Number of Blades
Most commonly, propellers with three blades are utilized. They deliver strong overall performance and high speeds with greater efficiency. In contrast, four-bladed propellers typically offer improved acceleration, better lift at the bow and stern, and less ventilation. However, using four blades increases drag on the engine, leading to lower maximum speeds and altered handling characteristics.
Blade Surface Area
Blade surface area refers to the Most commonly, propellers with three blades are utilized. They deliver strong overall performance and high speeds with greater efficiency. In contrast, four-bladed propellers typically offer improved acceleration, better lift at the bow and stern, and less ventilation. However, using four blades increases drag on the engine, leading to lower maximum speeds and altered handling characteristics. total surface of the blades. The more blade surface area a prop has, the more water it pushes, for an exceptional hole shot and increased planning efficiency. Too much can create a substantial amount of drag, which can restrict the engine RPM, which can cause unfavorable boat handling issues.
Blade Geometry
The true shape of the blade (or ear). Adjusting the blade's shape, diameter, or pitch will lead to various performance features. The pitch is approximately 150 +/—50 RPM.
Cup
When used with the correct measurements, the small curved lip on the blade tip and/or trailing edge helps reduce ventilation and propeller slippage. This allows for higher mounting heights and greater bow lift, which limits the engine's ability to create and maintain the proper RPM at a specific pitch.
Rake
Rake refers to the angle of the blades in relation to the propeller barrel or center, measured in degrees. A high rake propeller is optimal for high engine mount applications, as it helps reduce ventilation and enhances bow lift. Excessive rake can strain the engine and diminish the hole shot, leading to poor performance and maneuverability. Conversely, a propeller with a low rake angle exerts less stress on the engine, resulting in a better hole shot and a higher wide-open throttle (WOT) operating RPM.
Ventilation
Ventilation happens when air is sucked in around the propeller blades. While this increases RPM, it leads to a reduction in speed because the propeller blades fail to engage effectively with clean water. This situation often occurs during sharp turns or in particular water conditions, such as following seas.
Controlled ventilation offers advantages by allowing the engine to reach higher RPMs during quick acceleration. This feature is purposely integrated into certain propellers, especially those used in two-stroke outboards. For instance, small holes are added to the sides of the propeller barrel, facilitating exhaust intake around the blades during the hole shot. This design permits two-stroke engines to achieve the elevated RPMs needed for optimal hole shot performance. Conversely, four-stroke engines typically do not need this feature.
Controlled ventilation can be advantageous as it assists the engine in achieving higher RPM during rapid acceleration. This feature is specifically designed into certain propellers, primarily used in two-stroke outboards. For instance, small holes are incorporated on the sides of the propeller barrel to allow exhaust to be intentionally drawn in around the blades during a whole shot. This design helps two-stroke engines reach the elevated RPM necessary for optimal hole shot performance. In contrast, four-stroke engines typically do not require this feature.
Controlled ventilation can be beneficial, though it helps the engine gain RPM during hard acceleration. This is engineered into certain propellers and is most usually used on two stroke outboards. An example of this is the small holes in the side of the propeller barrel which allow exhaust to intentionally be drawn in around the blades at the whole shot. This helps two stroke engines generate the higher RPM they need for proper hole shot performance. Four stroke engines typically don't need them.
Cavitation
Cavitation occurs when the pressure on the water surrounding the blade decreases sufficiently to transform it into vapor, resulting in bubble formation. When these bubbles collapse, they can cause a cavitation burn that damages the propeller's surface, leading to performance issues. This condition may also result in higher engine RPM, which is frequently mistaken for ventilation.
Slip
The energy wasted by a propeller shows that the distance traveled in one full revolution is shorter than its pitch. This inefficiency is frequently expressed as a percentage. Each propeller line is purposefully constructed with a defined slip amount to attain various performance features.
Hole Shot
The hole shot refers to the rapid acceleration of the boat, transitioning from a complete halt or minimal speed until it achieves plane status. During this phase, the engine and propeller operate at their utmost capacity.