What is RPM at WOT?

RPM is Revolutions per Minute, as measured by your engine’s tachometer and WOT is Wide Open Throttle. It is important to know what this reading is in order to determine if your engine is working efficiently with your current prop selection. Every engine has a recommended operating range at WOT and you need to ensure your engine is operating within this range. Propeller size will affect your RPM at WOT.

Should I go from a 3 blade to a 4 blade prop?

If you look at a propeller from behind, and visualize a circle that the blade tips would draw, you will see that the blade of a 3 blade prop covers about 50 -55% of the circle. (This is called diameter area ratio, or DAR). You can add thrust within this drive circle by increasing that percent (to say 60 – 65%) by adding a 4th blade. When you look at a four blade prop you will notice that more of this area is covered because of the extra blade. That means more push contact with the water. Think of it as going to wider tires on your car. More traction for your car and more traction for your boat. Just as wider tires on your car usually do not alone increase top speed and can actually reduce it, the same usually holds true for a four blade prop. One big advantage, however, is that the added thrust from a four blade prop can keep your boat on a better planing angle in mid-range and lower RPM’s, which as you can imagine translates to better fuel economy.

Does prop material make a difference?

As a rule, a stainless-steel prop (assuming the correct pitch and diameter) will make your boat go faster — up to 2-3 knots on some boats. Stainless steel is stronger and can be made thinner, allowing more speed. Stainless steel also flexes less and keeps its shape at higher speeds. The downside to stainless-steel props is cost, about three times more than an aluminum prop, and more expensive repairs. Also, in a severe strike, they may cause drivetrain damage because they won’t deform as easily.

Do composite and aluminum props flex?

Of course! All propellers flex. What is often missed is that flex is a good characteristic. For example, if a prop flexed under the load of acceleration, it would actually be reducing its pitch, which in turn would produce a faster acceleration. A problem would occur only if the prop failed to return to its specified pitch once up to speed with the load reduced. The measurement of this two-way propeller movement is called “yield.”

The question people should ask is: “should I be concerned with a low yield number in a composite and aluminum prop?” In this regard, the yield numbers for aluminum and composite are about the same and high enough to handle the loads they designed for. Stainless (being much stiffer) has a higher yield number and is well above basic requirements.

What about composite Props?

When propellers made of composite, or plastic, first came on the market over 14 years ago, I was very skeptical that they could match an aluminum prop in strength and performance. Today, while not all composites are created equal, a couple of manufacturers use space age composites to exceed the strength of the old traditional props. One uses a long-fiber nylon and carbon composite to deliver outstanding strength and performance. I suppose this should not surprise us as many commercial turbo-prop (propeller powered by a jet engine) aircraft now use composite props and ‘Formula I’ race plane rules specify composite props over aluminum, because “aluminum props are subject to catastrophic failure.”

So far, composite manufacturers have held their prices down to about the same as aluminum, making them an excellent value.

My pick of the composites is a prop called “Piranha.” This is not simply due to superior performance, but because the hub is guaranteed for life and you can easily and inexpensively replace individual blades should you break one. Applications range from 8 to 300 horsepower.

What prop can I buy to improve my hole shot and top speed?

Probably none! These are two separate objectives that require a separate specialty prop to accomplish each one. For example, while a five bladed propeller could get you onto plane quicker, it will usually knock three to five mph off your top speed.

Should I spend the extra money for a stainless propeller?

In most cases, by simply making a direct conversion to stainless in the same size as your aluminum prop, you will notice an improvement in both acceleration and top speed. The reason for this is very simple, but frequently misunderstood. Stainless is seven times stronger than aluminum. Propellers don’t have to be that much stronger so manufacturers can make them thinner and still be two or three times as strong. Thinner props cut through the water easier and this of course translates to better performance.

Stainless propellers generally cost a couple of hundred dollars more than an aluminum or composite propeller.

There are two situations where I don’t recommend stainless over aluminum or composite: smaller outboards in pleasure applications, (because the prop can be stronger than the gear case parts) and for very occasional boaters who are happy with the existing performance of their boat.

How can I make my boat come on plane faster?

There are many factors that can cause a boat to have difficulty coming onto plane. Consider for example, your total boat weight, weight distribution, engine trim, hydrofoil, and transom tabs before investing in a new propeller. To assist in the correction of on plane problems, you may also need a different propeller. Your first choice should be a propeller with more blade area. Keep the pitch the same, but provide more blade area either through a slightly larger diameter or an extra blade. In cases where this would not be enough, you may have to trade some top speed for a better bottom end through reducing the pitch a couple of inches.

Why not run a damaged propeller?

Continuing to use a damaged propeller can cause damage to the gearcase and ultimately the power head of your motor. When a propeller has sustained damage, it will not spin true, thus creating excessive vibrations that will transfer all the way into your motor. A damaged propeller will also not perform as well as a new propeller because the damaged parts of the blade can degrade hydrodynamic efficiency and result in poor performance and fuel economy.

Should I repair my prop or buy a new one?

Most small dings or bends in an aluminum prop can be repaired for a reasonable price. If you do repair, make sure the shop does not file down the blade edges thereby reducing diameter. If your damage includes bites or chunks out of the bade, you should consider a new prop.

Keep in mind that while aluminum propellers can be welded back to look like new, there is significant strength loss when you do. Since a light tap could then put you back where you started from, you shouldn’t spend money on an expensive repair. Stainless props cost more to repair than aluminum because the material is more difficult to work with, however, once properly repaired, they can be as good as new.

How do I get the most value for my money?

You can get the best value for your money by making sure you have the right propeller for your boating application. Don’t be too concerned with prop costs because the biggest bang that you can get for the buck, when it comes to boat performance, is with the propeller. Remember that a slightly incorrect type or size of propeller can seriously reduce several aspects of your boat’s performance.

Of course this doesn’t mean you should spend money unnecessarily. The answers to the remaining most commonly asked questions, should help you understand a lot more about propellers and to make a decision as to which propeller could be best for your own boat.

If you are still uncertain you can consult one of our experts at Ace Propeller.

Do composite and aluminum props flex?

Of course! All propellers flex. What is often missed is that flex is a good characteristic. For example, if a prop flexed under the load of acceleration, it would actually be reducing its pitch, which in turn would produce a faster acceleration. A problem would occur only if the prop failed to return to its specified pitch once up to speed with the load reduced. The measurement of this two-way propeller movement is called “yield.”

The question people should ask is: “should I be concerned with a low yield number in a composite and aluminum prop?” In this regard, the yield numbers for aluminum and composite are about the same and high enough to handle the loads designed for. Stainless (being much stiffer) has a higher yield number and is well above basic requirements

Boat propeller cavitation

Have you ever run your finger along the face, or edge, of a prop and felt a pitted area? If you have, then you know what cavitation can do to a prop. Given enough use, that pitting will only get deeper and you will end having to replace the prop.

With your prop turning 4000 rpms how are you to know if you have power-robbing and prop-damaging cavitation?

Cavitation very commonly occurs on damaged, or imperfect, propellers and can occur if an attempt is made to transmit too much power through the prop. At high rotating speeds or under heavy load (with high blade lift coefficient), the pressure on the inlet side of the blade can drop below the vapor pressure of the water, resulting in the formation of a pocket of vapor, which can no longer effectively transfer force to the water.

In my manner of thinking, cavitation could be defined as the phenomenon of the formation, rapid collapse, and subsequent implosion of vapor bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. As these bubbles collapse, energy is released in the form of a shock wave that can, and often does, damage the surface of the material in question (Stretching the analogy to a screw, you might say the water thread ‘strips’.)

The true cause of cavitation can arise from several factors, but we see them occur most often, as a result of leading edge imperfections, such as, nicks, dings, scratches, bends, etc.. That said, they can, also, be caused by improper geometry, or upstream imperfections related to the hull, such as, hull design/configuration, hull imperfection, incorrectly installed accessories/appendages, etc.. Since there are so many possible causes, diagnosing the problem should really be done on a per case basis.

Cavitation wastes energy, makes the propeller “noisy” as the vapor bubbles collapse, and most seriously, erodes the prop’s surface due to localized shock waves against the blade surface.

A similar, but quite separate issue is ventilation, which takes place when air is introduced to water around, or to the water flow fed to, a propeller. This can be caused by a number of different sources, such as, porting, over-and-thru hub propellers, tunnel hulls, extreme motor elevation, excessively high trim angles, stepped hulls, or even hull appendages (transducers, pick-ups, and the like). As the propeller meets the aerated water, the water’s flow attachment to the propeller’s respective working surfaces, is detached. As the water detaches, the propeller’s loading is reduced, and the torque applied to the propeller through the shaft can more easily spin the propeller to a much higher rpm even at the same given power input. This, not only, causes the motor to rev easily, but it reduces the thrust provided by the propeller, slowing the boat’s speed and/or acceleration, as well as, reducing the propeller’s control over the boat (blow out on turning, on holeshot, etc.).

Specifically what happens in cavitation is this: Vapor gases evaporate into the cavity from the surrounding medium; thus, the cavity is not a perfect vacuum, but has a relatively low gas pressure. Such a low-pressure cavitation bubble in a liquid begins to collapse due to the higher pressure of the surrounding medium. As the bubble collapses, the pressure and temperature of the vapor within increases.

The bubble eventually collapses to a minute fraction of its original size, at which point the gas within dissipates into the surrounding liquid via a rather violent mechanism, which releases a significant amount of energy in the form of an acoustic shock wave and as visible light. At the point of total collapse, the temperature of the vapor within the bubble may be several thousand Kelvin, and the pressure several hundred atmospheres.

Cavitation can significantly damage moving parts, and is usually an undesirable phenomenon. It is specifically avoided in the correct design of props and that is why prop fabrication and prop repair must be relegated to the experts.

If you have questions about cavitation or need help with your propeller installations, contact the experts at ace propeller 1-866-799-7767

What about composite props?

When propellers made of composite, or plastic, first came on the market over 20 years ago, I was very skeptical that they could match an aluminum prop in strength and performance. Today, while not all composites are created equal, a couple of manufacturers use space age composites to exceed the strength of the old traditional props. One uses a long-fiber nylon and carbon composite to deliver outstanding strength and performance. I suppose this should not surprise us as many commercial turbo-prop (propeller powered by a jet engine) aircraft now use composite props and ‘Formula I’ race plane rules specify composite props over aluminum, because “aluminum props are subject to catastrophic failure.”

So far, composite manufacturers have held their prices down to about the same as aluminum, making them an excellent value.

My pick of the composites is a prop called “Piranha.” This is not simply due to superior performance, but because the hub is guaranteed for life and you can easily and inexpensively replace individual blades should you break one. Applications range from six to 300 horsepower.

How can I make my boat come on plane faster?

There are many factors that can cause a boat to have difficulty coming onto plane. Consider for example, your total boat weight, weight distribution, engine trim, hydrofoil, and transom tabs before investing in a new propeller. To assist in the correction of on plane problems, you may also need a different propeller. Your first choice should be a propeller with more blade area. Keep the pitch the same, but provide more blade area either through a slightly larger diameter or an extra blade. In cases where this would not be enough, you may have to trade some top speed for a better bottom end through reducing the pitch a couple of inches

Best wishes for a safe and happy holiday!

Best wishes for a safe and happy holiday! Thank you for your patronage and look forward to serving you in 2015!
Safe and Happy Boating on your next outing on the water.

From your Ace Propeller Team!

Should I repair or buy a new boat propeller ?

Most small dings or bends in an aluminum prop can be repaired for a reasonable price. If you do repair, make sure the shop does not file down the blade edges thereby reducing diameter. If your damage includes bites or chunks out of the blade, you should consider a new prop.

Keep in mind that while aluminum propellers can be welded back to look like new, there is significant strength loss when you do. Since a light tap could then put you back where you started from, you shouldn’t spend money on an expensive repair. Stainless props cost more to repair than aluminum because the material is more difficult to work with, however, once properly repaired, they can be almost as good as new.

Another option is Piranha propellers ; they were developed with three things in mind: durability, performance and affordability. A key feature is that the blades are replaceable. You can change the diameter and the pitch, save on the costs involved with propeller repairs, not to mention the potential damage to your gear case. With Piranha you can have some spare blades in the boat for a quick and affordable repair.

How much should I spend on a boat propeller

I advise boaters to spend as much as it takes to get the right propeller for their boating application. Don’t be too concerned with prop costs because the biggest bang that you can get for the buck, when it comes to boat performance, is with the propeller.

Remember that a slightly incorrect type or size of propeller can seriously reduce several aspects of your boat’s performance.

Of course this doesn’t mean you should spend money unnecessarily. The answers to the remaining seven most commonly asked questions, should help you understand a lot more about propellers and to make a decision as to which propeller could be best for your own boat.

In looking at these questions keep in mind that propellers are always referred to by two numbers. The first number is the ‘diameter’, or straight line distance in inches, from a blade tip to the center of the of the hub, times two. The second number is the ‘pitch’, or theoretical distance in inches that the propeller would travel forward in one single revolution.

Propeller diameter available for engine with larger gearcase

Another title could have been Boat propeller Diameter on command trust or big foot motors.

Many factor will influence rpm and diameter is one of them. I am seeing in the last several seasons some large pontoons being pushed by 60 hp engines that are command trust /or Bigfoot. This means that the gear case is in a larger category

The problem is that the lowest pitch props available for a bigfoot 60 hp would be 14×11 and reaching the minimum recommend RPM range becomes impossible….Same engine with a non-command thrust or not a big foot can runs a 2” smaller diameter propeller and a lower pitch is available
the key is the fact that it is also 2 “ shorter in diameter
In this case the lowest pitch available becomes a 12×9 an increase of about 900RPM

At Ace propeller our tech support team will be happy to answer any questions relating to propeller selection.

Piranha boat Propeller absorbs shock

The Piranha modular design allows for blades to be replaced due to damage or to be re-pitched for performance. The key to the patented Piranha boat propeller is the hub. The center hub is made from a high-strength aluminum core, over molded with our specially-formulated composite material.
The Piranha blades are designed to absorb the shock of a propeller strike, which virtually eliminates lower unit damage. The Piranha hub is so strong that it is guaranteed for life, “you damage it, we will replace it.” The Piranha design also eliminates spun propeller hubs.
The replaceable blades are manufactured from a specially formulated high-strength aerospace composite material. The manufacturing process is so precise, that the blade shape and pitch distribution is superior to Stainless Steel and Aluminum. Blade balance is no longer a problem as the Piranha Propeller blades are balanced to 2 times the industry standard. The precise balancing reduces lower unit damage caused by vibration.

Safety on the waterways

Courtesy on the Water.

For all of us to enjoy our boating experience, courtesy and the rules of the waterways are extremely important. From kayakers and canoers, to the fishing boats to the cruisers and the sailers, knowing when to give way, when to slow your boat down to reduce your wake or when to get out of the way are all extremely important. Sometimes common sense plays a big factor to keeping the waterways safe. I know when I am in a 24 foot boat and I see an ocean bound freighter coming down the St. Lawrence, I get out of the way! These freighters take an extremely long distance to slow or even come to a stop. The same for larger cruisers, they do not stop on a dime. As the captains of larger vessels are responsible for their safe progress through the water, common sense is best used when operating a smaller vessel to stay clear and choose your moments when to cross a channel that may mean crossing in front of a larger vessel. Managing your wake of your boat is also your responsibility. Come off plane or reduce your speed when passing a small fishing boat or canoe or kayak to avoid swamping the craft or possibly knocking the occupants out of their boats. Wake board boats need to understand this as well and respect the other crafts on the water as well as the possible damage that large wakes do to the shoreline and docks all along the shoreline. There are more and more of the wakeboard style boats and the type of water sports enjoyed with these type of boats is growing in popularity! Please be careful and use common sense out there. That way everyone can enjoy the days we get to spend out on the water.

I suggest you review the safety requirements for operating your boat and make sure you have all the recommended gear on board for your safety and the safety of your passengers. This includes having a spare propeller on board and the tools to change your prop if you should hit something in the water.

Enjoy the season and your time on the water!

Kevin Rougeau

Spring boating season 2017

Start of the boating season 2017 for those of us who experience a winter! A lot of us are waiting for the nicer weather to show up! Record rainfalls, lots of flooding and swollen riverbanks has delayed some of us from safely accessing launches. The nicer weather is coming soon so take this time to get ready!!!

Whether you’re a seasonal boater down south or from the north, it’s always a good idea to have your motor properly serviced by a qualified dealer and a licensed mechanic. If your boat’s been stored for a period of time, this would involve the first start up, blowing out the fogging oil from last fall’s winterization or storage, making sure all hoses and lines are in good shape (no cracks or leaks), oil has to been changed if you have a 4 stroke or oil levels are full for a 2 stroke. Gear case oil needs to be checked and changed. Changing the spark plugs is always a good idea (at least every 2 seasons) and make sure the engine has proper cooling by changing your impeller every couple of seasons. Your qualified mechanic will ask you all the right questions and help to ensure your boat and motor are running right for the first trip out and for the whole season. If you are a do-it-yourselfer, there is plenty of information on the web and lots of instructional videos on YouTube to show you how to maintain your boat and motor. Make sure you have good clean gas for the initial startup. Fill up your tank so that you are not just running last year’s gas through your motor.
On a regular basis, you should check your trailer and lights particularly after your trailer has been sitting for a while or stored for the winter. Make sure brakes lights, turn signals and running lights all work. Lubricate the wheel bearings on the trailer. Most trailers have bearing buddies that can be easily greased or you may want to consider repacking the wheel bearings. It is also extremely important to ensure your tires are inflated properly and that they do not show signs of excessive wear. Check the requirements stamped on the side of the tire as to proper inflation pressure.

Also check your safety gear on board! We should have all taken some sort of boating safety course. There is a Coast Guard guide which lists all the safety gear that you should have on board. This includes the following but you should check the Coast Guard requirements before you head out on the water:
• Good strong paddle
• Sound/signaling device
• Flare
• Anchor with sufficient rope, 50 ft. minimum
• Lifejackets for everyone on board
• A throw safety cushion and floating rope
• Boat fenders/bumpers and dock tie lines
• Bailer and/or operating bilge pump
• Waterproof flashlight with good batteries
• A spare prop and tools to change it!

CHECK THE COAST GUARD REQUIREMENTS

Check the condition of your propeller. The propeller blades should not be bent or damaged as a damaged blade will affect performance and efficiency of the propeller. Make sure the leading edges of the blades are smooth and not badly chipped.

Remember that when water levels are high in the spring a lot of debris gets dragged off the shore so be careful out there and keep your eyes open to avoid any costly strikes with floating debris.

Have a safe and fun filled boating season this year!
From the Ace Propeller Team!

We can help you select the correct propeller

We can help you select the correct propeller the more info we know the more accurate our recommendation

Motor type and manufacturer
Year and horsepower of motor
Length and type of boat
Any current prop info will help. Diameter, pitch and type of material
WOT (wide open throttle) RPM reading with current prop is the best way to know how we can improve your performance
WOT (wide open throttle) RPM reading with current prop if you can answer some or all of the prop info

Also what kind of boating do you do most often. Watersports…cruising ..top speed ?

We will then be able to help you with a more accurate recommendation.

Technical Boat propeller lingo

Pitch – the theoretical distance in inches that a propeller moves forward in one revolution. Think of a screw in wood. If you increase the angle of the threads, it will move further into the wood in one turn.

Diameter – the diameter in inches of the circle that the blade tips will cut. Or, the distance in inches from a blade tip to the center of the prop, multiplied by two.

Propeller Size – props are named by the diameter inch number, followed by pitch inch number (i.e. 14 x 19 or 14″ diameter x 19″ pitch).

Blade – the part of the prop that acts as a paddle.

Elliptical Blade – one that’s elliptical in shape.

Tapered Blade – a blade that is tapered in shape. (As opposed to round ear or elliptical.)

Cupped Blade – a blade that has a lip built into its trailing edge. (Most do) The lip generally helps a prop hold water. It also adds the equivalent of about 1/2-inch to one-inch of pitch.

Polished – a prop that has had the steel polished from a dull to a shiny finish.

Hub – the center part of the propeller. The hub, as an actual part, is the piece that fits inside the barrel of a prop and what the shaft slides into. If you strike something, the hub breaks free of the barrel and spins so that you don’t damage the drive-train. The word hub is also often referred to as the size of the barrel. (i.e. 4.5″, 4″, 3″, 2.75″)

Skew – a blade whose shape sweeps in a curve that follows its rotation is said to have a skew.

Rake – if a blade sticks straight out of a hub, in other words, is perpendicular to it, that prop has no rake, or zero rake. If the blade leans back more towards the trailing edge of the prop, it is said to have rake. If it leans way back, it is a high rake prop. Rake can be measured in degrees.

Wise boat propeller advice

I advise boaters to spend as much as it takes to get the right propeller for their boating application. Sometime it means Stainless ( 300hp and up ); sometimes it means 3 blade ;sometimes it means 4 blade; Don’t be too concerned with prop costs because the biggest bang that you can get for the buck, when it comes to boat performance, is with the propeller.

Remember that a slightly incorrect type or size of propeller can seriously reduce several aspects of your boat’s performance.

Of course this doesn’t mean you should spend money unnecessarily. we can help you understand a lot more about propellers and to make a decision as to which propeller could be best for your own boat.

In looking at these questions keep in mind that propellers are always referred to by two numbers. The first number is the ‘diameter’, or straight line distance in inches, from a blade tip to the center of the of the hub, times two. The second number is the ‘pitch’, or theoretical distance in inches that the propeller would travel forward in one single revolution.

Happy new year of boating

Best wishes for a safe and happy new year! Thank you for your patronage and look forward to serving you in 2017!
Safe and Happy Boating on your next outing on the water.

From your Ace Propeller Team!

Happy holidays

Wishing you and you families best wishes for the Holliday seasons

From the Ace propeller team

How to find the best propeller for my boat

Finding the right prop for your application is not as easy as you may think. In fact, it is our experience that proper prop selection is one of the most difficult tasks in boating to make sure you are getting optimum performance. Mistakes can be costly in terms of fuel consumption, drive train wear, prop longevity and speed. The right pitch and diameter is not the end of it, but rather just the beginning of the process. There are numerous other aspects to prop selection including rake, cup, surface area, material and the number of blades.
We at Ace propeller can help you choose the best prop for your application

call our tech support at 1-866-799-7767

Boat propeller damage

As gas prices continue to creep up we are getting more and more enquiries from customers on how to improve performance with regards to fuel efficiency. A slightly damaged blade where the leading edge of the propeller has been damaged by running through some sand or gravel. The propeller blade edge should be filed smooth. There should be no dings or chips as these imperfections in the leading edge cause air bubbles and cavitation in the blades of the propeller and reduce performance by reducing the efficiency of the propeller. If the blade is too damaged it will have to be replaced as running a prop that is out of balance because of damaged blades can reduce performance and actually cause damage to the foot of your motor. At the end of the day this costs you at the gas pump or possibly at the repair shop!$$$
The Piranha propeller with the replaceable blade system is a great choice as you can replace one damaged blade at a time for a fraction of the cost of repairing an aluminum propeller or having to replace the propeller by buying a new one.

Inspect your prop regularly! It will save you money and ensure your boat is performing properly.

High altitude will affect performance

Boat propellers are available in several materiel, pitch and diameter and the expert at Ace propeller can help you select the correct boat propeller that will work best at the altitude that you are boating at .Many factors can reduce your RPM in many ways I.E. upgrading to better materiel, increasing the diameter and/or pitch, upgrading to a 4 blade, cupping ect. However the worst effect is altitude…Lack of oxygen makes for terrible performance.

Here is a chart that can help

Altitude chart versus minus in pitch required
3000ft…-1 in pitch
4000ft…-2
5000ft…-3
6000ft…-4
7000ft…-5
8000ft…-6
9000ft…-7 in pitch

I would suggest a composite propeller by Piranha and you can have a set a of blades with a lower pitch for boating at high altitudes.

Piranha composite propellers are superior to any aluminum. Piranha propellers were developed with three things in mind: durability, performance and affordability. A key feature is that the blades are replaceable. You can change the diameter and the pitch, save on the costs involved with propeller repairs, not to mention the potential damage to your gear case. With Piranha you can have some spare blades in the boat for a quick and affordable repair

We also sell the hi-grade aluminum propellers from Michigan wheel and Solas

And of course Powertech Stainless and aluminum propellers

You can call 1-866-799-7767 to place an order

Ace Propeller