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When you have the right propeller and it is working properly, your boat engine will run within the manufacturer’s designed RPM at Wide Open Throttle (WOT). If that is not the case, you may need a new propeller. Here is how to test your propeller performance:
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Are you satisfied with your current prop performance (apart from any damage that may be requiring you to purchase a new prop)?
Once you get to the next page, you can narrow the selections by various features. Use the information below to help make your selections
The type of boat you have and the performance you want from it will determine the number of blades you choose.
Pitch is the theoretical distance a propeller travels in one revolution.
Pitch affects the performance of a prop more than any other aspect and is measured in inches - as such, you will hear about "high pitch" or "low pitch".
If your pitch is too high, it will "lug" the engine, reducing both top speed and performance. If your pitch is too low, it will cause the engine to exceed the specified RPMs at the top end. Sustained operation in either of these situations will cause catastrophic damage to the engine.
Boat propellers are made of aluminum or steel and both have their advantages and disadvantages. Unlike other prop features, the choice of material is really more a matter of preference (vs. requirements based upon boat style, etc).
Cup is the added curved lip on the trailing edge or blade tip. This added curvature will increase pitch when added to the trailing edge and increase rake when added to the tip.
Cupping a propeller will cause a decrease in RPMs. The actual amount of RPM decrease depends on where, how much and the quality of the cupping.
Cupping also tends to decrease ventilation and allows higher trim angles and transom settings. It is typically used on propellers when higher performance if required.
Rake is the measurement of the angle of the tilt of the blade’s tip toward or away from the gearcase. The angle is measured on a line extending from the center of the hub through the center of one blade.
You can know if your blade diameter is appropriate by a few easy signs:
Boat propeller blades can rotate either to the right or to the left. Right-hand rotation is the most standard while left-hand rotation is mainly used for one engine in a dual motor application to balance performance across the two engines.
The hub, as the name implies, is the inner core of the boat propeller. It slides over the propeller shaft and is the point onto which the blades attach. Always be sure that the prop and the hub have identical splines.
A fixed hub is most common and has the hub integrated into the propeller core as one unit. This is the most cost-effective solution for running a single prop.
If you need to change props for different conditions, you will want to consider a removable hub. This allows multiple props to fit onto one hub, reducing the cost of needing multiple props.
Being aware of some common problems can also help guide uou in selecting the right propeller for your needs.
This occurs when exhaust gas or surface air is drawn into the blades of the boat propeller. This causes the boat to lose speed and RPMs to climb rapidly, leading to excessive slippage. Slippage is essentially the difference from the theoretical pitch to the actual pitch. You will want the minimal amount of slippage for top performance.
This occurs when there is an area of low pressure caused by the inability to move through the water and then the water around the boat propeller begins to bubble. The bubbles collapse when they reach an area of higher pressure around the blades. Cavitation and changes in pressure can result in erosion on the face of the boat prop blades, ventilation and/or slippage.
< Severe cavitation damage on a boat propeller
Seemingly soft surfaces can reduce a boat’s fuel economy and overall efficiency. The damage can lead to cavitation and irregular leading edges on the boat prop blades.
Boat propellers can become damaged by hitting hard items, such as rocks, in shallow waters.
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Follow these tips to keep your boat propeller in top shape: