Though they’re under the surface, your propeller is one of a boat engine’s most critical components. The wrong propeller can cause performance issues with your boat and cause extra wear on your expensive engine.
Most boat stores have rows and rows of yacht propellers. It can be intimidating to make a decision when you aren’t familiar with the “prop” terms or if you’re not sure how to address the problems you’re facing.
Propeller Terms to Know
When you first start out boating, you have to become familiar with a whole new set of terminology. Propellers are no different. Before picking out the right propeller for your engine and boat, you should familiarize yourself with the common terms.
You can tell what size the propeller is with two numbers. The first is the propeller diameter, and the second is the pitch. You can find these numbers stamped on the propeller.
The diameter is the length of the propeller doubled. Smaller boats typically need smaller propeller dimensions. Some performance speed boats also require smaller propellers.
The second number, the pitch, is the forward motion in inches per rotation of the propeller. The pitch is more of a theoretical number since about 10-15% of the motion between the propeller and the water “slips.”
Pitch Up & Pitch Down
A higher or lower pitch affects your rpm. The lower the pitch you have, the higher the rpm since the propeller will require more rotations to exert the same amount of power as a higher pitch.
Going up or down a pitch depends on your performance goals, hull size, and boat weight.
The rake is the slant of the propeller, either forward or backward from the hub. This slant affects the direction water is directed as it flows through a propeller. This affects how the boat rides. For example, a high-speed boat uses a rake to lift the front of the boat.
Cupping refers to blades with a curve to the edges of the blade. Think airplane propellers. This allows for a smoother water flow, better ventilation, and less slippage.
Having the wrong propeller can cause your engine to underperform and even cause damage. How do you know if your propeller isn’t the right one?
Common Propeller Problems
Whether your boat feels sluggish or you just want to improve its speed performance for water sports, there’s a lot your propeller can change about how your boat runs on the water.
To know how you need to change your propeller for the better, you first have to determine what’s causing your problem.
Over Revving and Under Revving
Check your owner’s manual for what the rpm should be for your particular engine. Having too high or too low of an rpm can cause permanent engine damage. You can fix this problem with a lower or higher pitch.
You may have the right propeller and pitch for a regular load. But, if you regularly haul skiers or tubers, or if you frequently carry heavy equipment, you may require a propeller with a lower pitch. That way, the extra weight on board doesn’t strain your engine and cause damage.
One way to cater to both situations is to have two propellers with different pitches—one for towing and regular usage.
If you travel by your boat to higher altitudes, you may need to compensate for lower oxygen levels. Oxygen levels can affect an engine’s performance. It can make them put out less power.
You can add on a propeller with a lower pitch to compensate for the higher altitude’s effects. A lower pitch makes it easier for an engine to meet the right rpm with less power.
If your prop encounters too much air, it causes a squealing noise, and it will cause your boat to slow down and over-rev. This can result from an engine mounted too high on the boat or from a poorly made propeller.
Sometimes a propeller that is worn out or has insufficient cupping also causes this problem. By switching to a better-suited, quality propeller, you can avoid this problem.
Outboard motors are typically made of aluminum or stainless steel because they’re cheaper to replace and easy to repair.
Inboard motors with bronze or nickel-bronze-aluminum alloy use aluminum or stainless steel replacement parts because they’re easier to source.
Aluminum is the most common propeller material because it’s affordable yet still suitable for most outboard motors.
Stainless steel propellers are on the higher end of materials. They cost more, but they provide more durability and better performance.
If you’re regularly going speeds over 50 mph or going over sand bars and oyster beds, you may want to consider investing in a stainless steel prop.
3-Blade vs. 4-Blade Yacht Propellers
Both propeller types work well with outboard and inboard motors. For overall performance, 3-blade propellers work well. If top-speeds aren’t critical, or for boats that are under-powered, a 4-blade propeller works well to give it an extra push.
Evinrude RX3 & RX4
The RX3 and RX4 Evinrude props positively impact your engine’s acceleration, pulling power, and cornering. With the right selection, you can improve your speed by 5-10 mph.
The RX3 is their 3-blade propeller, which is ideal for any boat type. The RX4 is their 4-blade propeller, which is perfect for larger pontoon crafts or for boats that face turbulent off-shore waters.
Evinrude props are an excellent choice for boaters who are serious about getting the most power out of their engine.
Find More Buying Guides
Now you have a better understanding of Evinrude propellers.
If you found this article helpful in deciding what kind of yacht propeller to buy, then you should check out our other buying guides.