An informative article about Inboard Boat Props
An informative article about Inboard Boat Props
An outboard propeller is exactly what it sounds like: a propeller that is used with an outboard engine.
When you buy an outboard prop for your boat, you are looking for a propeller that works best with your specific combination of engine and boat. There is no one-size-fits-all prescription for propellers.
The most important way a propeller should fit your boat is running within the proper wide open throttle (WOT) operating range. This is measured in horsepower per R.P.M. (revolutions per minute). Each engine's manufacturer will indicate the appropriate range.
The basic goal of the best propellers is to achieve the highest horsepower at the lowest R.P.M. This means you will avoid over-revving and damaging your engine while achieving maximum speed and power levels. Keeping horsepower too low will result in lugging.
Over-revving and the strain that an inefficient propeller puts on a boat's engine can even lead to premature engine failure.
There are, of course, other factors that complicate this simple equation. These include your specific performance goals for your boat and troubleshooting issues like ventilation and cavitation.
The primary factors you'll want to consider when looking for a propeller are:
Outboard props are almost always made of either aluminum or stainless steel.
Aluminum propellers are more common and often come pre-installed on boats. They are cheaper, but also more prone to dings and other damage.
Stainless steel propellers, while more expensive, last significantly longer. The blades are thinner and stiffer. This allows them to function better in the water and to stand up to repairs more easily.
Diameter, or distance from propeller blade tip to blade tip, is one of the primary measurements that determine propeller function. It is so important that engine manufacturers specify the diameter of propeller to use.
You should follow the manufacturer's instructions here. If you are unsure what diameter propeller your engine's manufacturer specified, you can follow our guide to find out without consulting your instruction manual.
When you see props described using two numbers, like 14x19, the first number is diameter and the second is pitch. Pitch describes the theoretical forward distance the propeller would travel in one revolution if there was no slip at all.
In reality, all propellers experience some amount of slip in the water, but a prop that is well-matched with your boat should have 10% slip or less.
Aside from diameter, which is prescribed by the engine's manufacturer, pitch is the most important thing to consider when choosing an outboard propeller.
Lower pitch allows for better hole-shot and acceleration as well as better low-speed pulling power, as the propeller will encounter less resistance. Because each revolution pushes the boat forward a shorter distance, though, the top-end speed will be lower. This may make a lower pitch prop ideal for ski or wake boating.
A prop with a higher pitch will be able to achieve a faster top-end speed, but it's hole-shot and low-speed pulling power will not be as great. Higher pitch also results in lower R.P.M. overall.
Each propeller is set to rotate either clockwise or counterclockwise. Most outboards require right-hand props or props that rotate clockwise. Dual outboards, however, typically need one right-hand and one left-hand (counterclockwise rotating) prop.
It is best to check your manufacturer's instructions to make sure the propeller you get rotates in the correct direction.
Most propellers have either three or four blades.
Three-blade propellers work well for general recreation boats. They help a boat to reach top-end speeds more easily. The lower resistance they have also increases fuel efficiency and lowers their effect on the outboard's R.P.M.
Four-blade props have more resistance, which gives them better traction and bite. They may also provide a smoother ride with less vibration. They do not reach top-end speeds as easily but have better hole-shot and acceleration and low-speed pulling power.
The increased resistance of a four-blade propeller also makes them less prone to ventilation. Four-blade props handle better on tight corners and in rough waters.
The rake of a propeller describes the angle at which the blades slant backward from the line of travel. Rake is typically between zero and twenty degrees.
A higher rake will lift the bow higher out of the water and increase the boat's top-end speed. Too high of a rake can put a strain on the engine.
Cupping is a relatively common feature of outboard props. It refers to a curved lip on the trailing edge of the blade, which gives the prop more bite.
Functionally, cupping on the top of the propeller works like an increased rake. Cupping on the side of the prop works like an increased pitch.
An added benefit of cupping is that using a propeller with cupping allows for the outboard to be trimmed. This brings the prop closer to the surface and reduces R.P.M.
Now that you know all the measurements and specifications that differentiate outboard propellers, you can decide which one suits your boating needs best.
It may be ideal to choose two different propellers with two different pitches so that you can achieve top-end speeds or great hole-shot as needed. Check out our wide selection of outboard propellers to find one (or two) that fit your boat and your needs best.
If you are in the market for outboard or sterndrive propellers, check out SOLAS propellers.
Outdoor activities have increased during the COVID pandemic. And, like a lot of recreational equipment, boat sales have exploded.
There are a lot of decisions to make when buying a boat. And people spend thousands of dollars every year upgrading their engine and components to increase their craft’s performance. But one of the easiest and most cost-effective ways to do so is by selecting the right propeller.
There are several characteristics to consider when choosing a new propeller or upgrading an old one. The most important one is the material used to construct it. A stainless steel propeller can increase performance and last a lifetime.
Keep reading to find out more about the many advantages of a steel prop and why it might be the right choice for your boat.
When selecting a propeller for your boat, there are three main things to consider:
Each of these has a lot to do with how your boat handles and performs, as well as how fuel-efficient it is. Let's take a look at each one in more detail.
Propellers come with between three and five blades. Five-blade props are usually reserved for very heavy vessels. Since they have the largest surface area, they require more power to turn, which eats up more fuel.
Three-blade propellers are the most popular since they combine speed with fuel efficiency. This is because they have less surface area and need less power to turn. While there is still some debate about this, three-blade props are generally known to run faster than ones with more blades.
Some people prefer four-blade propellers for their increased “grip” and handling. They can offer a smoother ride and steadier cruising speeds, as well as the potential for greater acceleration. But again, having more blades increases drag, which requires more horsepower and fuel consumption.
The diameter of a propeller is basically the width of the circle made by the blades. The size of the blades determines how much water they can push per rotation.
A propeller’s blades are designed much like the thread of a screw. The pitch is the amount the prop moves forward in one rotation. Pitch is very important because it determines the gear ratio between the boat’s engine and the water.
For optimum performance, you want your boat to operate within its wide-open throttle (WOT), which you should be able to find in the engine owner’s manual. If a propeller pitch is too low, the engine could run over its WOT and risk damage. If the pitch is too high, the engine will run far below its WOT, which also can strain its gears and components.
You will often find diameter and pitch indicated on the propeller, with diameter listed first. For instance, a 14" x 19" prop would be 14 inches in diameter and have a pitch of 19 inches.
Most boat propellers are made of either aluminum or steel. Aluminum is the most popular propeller material used today, partly because it is very affordable.
But stainless steel propellers, while more expensive, offer many advantages. Consider just a few.
Both aluminum and steel propellers are resistant to rust and corrosion. And aluminum propellers are very durable under regular usage and conditions.
But steel is much stronger than aluminum. It is an alloy of iron, with carbon and chromium added in to improve strength and make it less likely to fracture. Stainless steel props are not brittle like many low-end aluminum ones.
Steel props are much less likely to bend or break when striking underwater debris, like logs or sandy bottoms. And they are more likely to last longer than aluminum ones, even with regular use.
Another advantage associated with steel’s strength is its lack of pliability. Steel props will not flex like aluminum ones, even under the strain of heavy loads.
Less bend means more power is being transferred in propulsion, which means greater acceleration and maneuverability. This can be beneficial to any boater, but especially those pulling people on skis or other recreational equipment.
Aluminum propellers tend to be much thicker than stainless steel ones, in order to compensate for the deficit in strength. This increases drag and also diminishes performance.
Steel propellers are much more common on boats designed for saltwater. This is because of their ability to handle the power of bigger engines needed in the ocean.
One area where aluminum propellers edge out steel ones is the initial cost. Stainless steel propellers tend to be more expensive than aluminum ones, which can sometimes be found for under $100.
Steel propellers also are more difficult to repair if broken. But, while aluminum props are cheaper to fix, the repair cost can still come close to the price of a new propeller. This is less so the case with stainless steel, which negates the advantage of aluminum in this regard.
In short, a steel propeller’s longer lifespan and resistance to breaking can still make it a better bargain, even if you consider the difference in repair costs.
Now that you have an idea of the many advantages of a stainless steel propeller, you can begin shopping for one that is right for your boating needs. It can increase performance and efficiency while lasting a lifetime.
Deep Blue Yacht Supply was founded on the basic principle of ensuring our customers get the right product for their boating needs. Our staff has over 100 years in the marine propulsion industry and can help you select the best stainless steel propeller for your boat.
We carry a variety of steel propellers, accessories, and other boating hardware. And we will ship our products to almost any location worldwide!