Outboard Propellers and Prop Hardware

Outboard Propellers and Prop Hardware Resources and Information

Finding the right propeller for your outboard is critical for achieving peak engine performance. PartsVu is pleased to stock an extensive collection of outboard propellers and prop hardware to fit your marine engine’s exact specifications. Need help installing your propeller? We also regularly publish helpful resources, like this one over on our blog. 

Browse our entire selection of aftermarket outboard parts and products and accessories, or shop outboard propellers and prop hardware by category, including: 

• Solas Propellers
• Acme Propellers
• Michigan Wheel Propellers
• Propeller Nuts, Washers & Hardware
• Propeller Wrenches, Pullers & Tools
• Turning Point Propellers

Outboard Propellers and Prop Hardware FAQs

How do boat propellers contribute to a boat’s performance on the water?

Besides the tachometer, the propeller(s) is the most important thing on the boat because it is the only thing that moves the boat. Without the correct pitch and diameter, a boat will not perform. Propellers limit the RPM range that motors need to run in. They help control speed, fuel economy, lift, cornering, and hole shot. With such a wide variety of boat, motor, and weight combinations, there are hundreds of boat props to choose from.

Unique hull designs affect the way water flows across the bottom of a boat so having the technical knowledge of propeller design helps ensure that the best selection is made for a given boat. There is a vast difference in propellers’ performance; many consumers do not always understand the performance advantages of selecting a high-quality propeller like Turning Point.

Do the number and size of propeller blades affect boat performance?

Absolutely. Larger and more blades will perform better for work boats that need to push heavier loads. For racing, the high horsepower requires more torque, which leads to a change in diameter, pitch, and the number of blades.

Grabbing more water is what makes a boat propeller more efficient. More blades tend to reduce slip by submerging more of the blade surface area underwater. For multiple engine applications, Turning Point’s OS series has a larger blade diameter that works more efficiently than many of its competitors’ products.

What type of propeller maintenance should boaters do?

Routinely inspect boat propellers for larger knicks and make sure the blades are not bent. Also, remove the propeller every six weeks. Fishing line tends to wrap around behind the thrust washer, which can lead to a seal failure.

With a ball-peen hammer, tap the edge of the washer to knock it loose so the fishing line can be removed. When putting it back together, apply a light coating of grease on the splines.

How do I choose the right propeller for my outboard motor? 

The right propeller for your boat and engine combination is based in part on the wide-open throttle (WOT) operating range for your specific engine. This information is an intersection of horsepower and RPM and can be found in your owner’s manual.

An optimal outboard propeller will maximize your boat’s performance while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving and facilitate maximum horsepower with minimum RPM.

An outboard engine under load should reach the manufacturer’s recommended RPM at WOT, usually expressed as an RPM range. Your optimal propeller will deliver acceptable acceleration and top speed while still allowing your Yamaha outboard to reach its recommended revs at WOT. 

If you get this relationship wrong, premature engine damage is too often the result.

Your propeller decision-making process will include the following factors: pitch, diameter, aluminum or steel, blade number, rake, cupping, and rotation.

Pitch is a critically important factor when selecting a new propeller. Pitch is the distance the prop would travel forward after one complete rotation, assuming no resistance or slip. 

Lower-pitch propellers encounter less resistance facilitating faster rotation and enabling hole-shot and acceleration. However, because each propeller revolution generates less forward travel, the ultimate top speed will be lower at WOT.

Hole-shot and acceleration will be reduced with higher pitch props because the outboard propeller encounters more resistance. This said, additional resistance reduces the motor’s RPMs and top speed at WOT.

Generally speaking, increasing prop pitch lowers RPM, while decreasing prop pitch raises RPM.

If you need more speed, a higher pitch is generally the way to go. However, If you use a propeller with a too high pitch, the motor won’t have enough horsepower to turn it adequately, so the revolutions per minute will drop. Referred to as over-propping, it overloads the engine and causes excessive wear. Under-propping—fitting a propeller with too low a diameter or pitch—can damage your engine through over-revving. Under-propping will also adversely affect fuel consumption. 

Each outboard propeller has two numbers stamped on them – diameter and pitch. For example, a 14 x 19 propeller has a diameter of 14 inches and a pitch of 19 inches. The greater the diameter, the more resistance it will experience in the water. 

A larger diameter propeller reduces the RPM and top-end speed. On the other hand, smaller diameter propellers increase RPM and top-end speed. However, smaller diameter props slip more frequently and are not good choices if hole-shot or acceleration improvement is your goal. 

What difference does the number of propeller blades make?

Three Blades Are the most common propellers. They offer good overall performance, top speed, and efficiency for most applications. Four Blades Characteristically provide increased acceleration, enhanced bow- and stern-lift, and reduced ventilation. However, their increased surface area can create drag on the engine, resulting in lower top speeds and potentially different handling. Ventilation is when air is drawn in around the propeller blades. Normally, this increases RPM, but lowers speed, because the propeller blades aren’t biting “clean” water. This usually occurs during hard cornering or in certain water conditions, such as following seas. Controlled ventilation can be beneficial, helping the engine gain RPM during hard acceleration. Engineered into certain propellers, usually two strokes, ventilation can appear as small holes in the side of a propeller barrel. These allow exhaust to intentionally be drawn in around the blades at hole shot, helping two-stroke engines generate the higher RPMs they need for proper hole shot performance. Four-stroke engines typically don’t use built-in ventilation.

What is the propeller rake? 

Rake is the angle of the blades in relation to the propeller’s barrel, or center, and is expressed in degrees. A high-rake propeller is best suited for high engine-mount applications. It reduces ventilation and increases bow lift. However, too much rake can negatively impact handling and performance by straining the engine, which will decrease hole shot. A low-rake propeller causes less strain on the engine, resulting in a potentially better hole shot and higher wide open throttle (WOT) operating RPM.

What does the propeller pitch mean?

Pitch is the distance a propeller would travel in one full revolution as if traveling through a solid. Each inch of pitch is equal to approximately 150 RPM, plus or minus 50 RPM. The right propeller will allow your engine, under a normal to heavy load, to reach the upper portion of the WOT range specified by its manufacturer without exceeding it. A lower pitch will have greater acceleration and “pushing power” but a lower top speed. A higher pitch will provide less acceleration, but a greater potential for higher top speeds. Within a particular propeller series, as the diameter increases, the pitch generally decreases.