Family & Watersport Boats
The Reliance family of outboard props is also great for many family boats pulling towables and boaters who participate in watersports.
Excellent low-speed operation, providing higher thrust and control than conventional propellers on pontoons using T50-F115 outboards. Features an SDS design that requires no special hardware to function.
Harnesses the power of Yamahas high-thrust outboards for pushing heavy loads such as sailboats and pontoons, and provides outstanding reverse thrust. Standard on T9.9 and T25, optional on T50 and T60.
Maximizing Horsepower Minimizing Rpm
The right propeller for your boat and engine combination is based in part on the wide-open throttle operating range for your specific engine. This information is an intersection of horsepower and RPM and can be found in your owners manual.
An optimal outboard propeller will maximize your boats 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 manufacturers 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.
Pitch Prop Vs 19 Pitch Prop: Which Do You Need
by Kyle WUpdated on April 23, 2021.
Boat Safe is a community supported site. We may earn comission from links on this page, but we have confidence in all recommended products.
Your boat is very much like your car without proper maintenance and the right parts, it will give you issues and might leave you stranded while out fishing for bass. The difference between your boat and your car is that the parts arent quite the same.
While it will do you well to know how to change a flat on your car, when it comes to boating, propeller diameter and pitch are some of the most important terminologies. This is because its your propeller that actually drives the boat. So understanding a bit about it could save you a whole lot of headache down the road.
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What Is Hull Resistance
Resistance is the hulls natural tendency to drag through the water. Bare hull resistance is produced by skin friction of the hulls surface, waves created by the hull running through the water and the shape of the hull below the water. To the bare hull, the drag of appendages must be added such as rudders, shaft support brackets, shafts, depth sounder transducers, stabiliser fins, etc. However, the design of the lift surfaces of the hull also have a very significant effect. Designers work to ensure that the lifting characteristics give the hull the least resistance at normal operating speed.
Once this resistance is known, engine and gearbox specifications can be combined with maximum propeller diameter to determine the props minimum requirements. The vessels duty cycle, which is simply a judgement as to whether a boat is to be used for heavy or light commercial or pleasure purposes, then also influences a designers final specification.
Propeller diameter is first decided by the type of boat. A large-diameter slow-revving propeller is the most efficient type but this wont provide the necessary acceleration to get a sports cruiser onto the plane. Acceleration is achieved by increasing the rotation speed, which usually means a smaller diameter propeller. The fact that many modern sports cruisers have limited propeller clearance space is another reason for fitting smaller diameter propellers.
To Grip The Water And Push The Boat
The result is the engine RPMs going above the specs and hitting the rev-limiter. Its exactly like what happens when the prop hub gets spun
On the opposite end of the spectrum, if were to install a prop with too big of diameter and pitch, then the engine wont have enough power to spin the propeller up to the right RPM range.
Causing the engine to never reach wide-open throttle and if ran like this for a long period of time, can eventually wear out internal components of the engine prematurely.
Its important to note that there are methods of getting propellers to turn up higher without changing the prop. This is usually done by venting the propeller some props have venting holes towards the bottom of the prop.
These holes can be either plugged or have the plugs taken out allowing water to flow freely through the prop without having to be pushed off the blades of the prop, causing force against it.
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What Determines The Type Of Propeller Your Boat Needs
If youre new to boating, you may not have expectations around what type of performance you should get out of your engine/propeller combo. That said, there are numerous variables behind which prop is right for your boat.
Propellers can make such an impact on performance that your neighbor could have the exact same boat and engine, but if the prop is different, the two boats could yield different results.
There are so many fluctuations and options that you could literally make the same exact boat faster just by adding a different propeller.
Choices that affect this change in performance are:
Stainless is a stronger metal than aluminum, so this type of prop is tougher against damage. It also doesnt flex, so it holds its shape in the water and can increase the speed depending on boat and engine type.
Aluminum is a softer and less expensive metal, so these props are usually more budget-friendly. That said, they do tend to flex, which can hinder the boats performance and speed.
Other factors that make a difference in how your propeller performs are:
Choosing a propeller can be subjective depending on your performance goals, but different engines and hull designs do play into selecting the best prop.
Is Your Engine Over Or Under Revving
Selecting the correct prop should result in your engine running within the designed rpm range at Wide Open Throttle . Your owners manual should include this specusually 50005500rpm for an outboard or 4200-5000rpm for a sterndriveor your mechanic or dealer may know. Allowing your engine to under rev or over rev at WOT can result in engine damage. Over revving or under revving can be corrected by selecting a prop with a different pitch.
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Are More Blades On A Prop Better
Contrary to popular belief, many boaters think that propping their boat with a prop containing more blades equates to better performance. To an extent, this is true. However, we have to consider several other variables such as the physics of the boat, propeller, and the water.
The more a boat is submerged in the water, the more drag is created. In turn, the more contact we have with the water, the better overall control we have of the boat. Nevertheless, more water contact also means slower boat speeds.
This concept also applies to the number of blades that the prop contains the more blades a prop has, the more drag it creates, in turn giving us a lower top-end wide throttle speed.
Running the correct prop, in the long run, is going to save you some money because it improves your mid-range cruising performance. If you are running a small prop, you will burn more fuel running higher RPMs in order to stay on plane at a decent speed.
Running too big of a prop, on the other hand, means that you will never hit wide-open throttle and this will eventually lead to carbon build up along with poor performance.
With the correct prop, we can cruise at the optimal mid-range RPM while simultaneously burning the least amount of fuel possible. A win-win for both your fun, wallet, and boat!
Stainless Steel Propellers Vs Aluminum Or Plastic
Most boat propellers are going to be one of these three materials. Aluminum props tend to be the most common. They are lighter and cheaper and can do a great job. However, stainless is definitely stronger. Stainless is also able to have thinner blades. If you want a top quality boat propeller, stainless steel is probably what you want. Most boats come with aluminum propellers. Large boats like yachts and small fishing boats alike.
Plastic props are more common on small boats. They require less power and the prop will do less work. The propeller blade on a plastic prop is going to be flimsy, as you might expect. Heavier boats cant use these. Theyll have more drag than the prop can handle.
For optimum performance, stainless steel props are best. The boats performance will reflect this. However, you may see increased fuel efficiency with a lighter aluminum prop. Much of it depends on the type of boat and engine you have.
Basically, a stainless steel prop is going to last longer than the others. Up to five times longer, in fact. It can stand up to more abuse. Youll be less likely to need to replace it as soon as another type.
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Tips On Choosing The Right Propeller For Your Boat
Does your boat take a long time to get up on plane? Maybe not hitting the top speed you think you should? Are you looking for better all-around performance and fuel economy? Apart from keeping your boats hull clean and your engine tuned, selecting the right propeller is one of the easiest actions you can take to get the most out of your boat.
First of all, note that the primary criterion for selecting a propeller is to make sure it allows the engine to turn up to a speed within the range specified by the engine manufacturer usually within 500 revolutions of absolute top rpm. This ensures a long life for the engine, neither lugging it down nor letting it over-rev. Your engine probably came with a propeller that achieved that basic requirement, but you can select a variety of props that will allow the engine to turn up yet have differences in pitch and number of blades, plus possess more subtle characteristics. For example:
Expressed with two numbers, diameter and pitch, with diameter always stated first. Diameter is two times the distance from the center of the hub to the tip of any blade. Smaller prop diameters generally go with smaller engines, or with fast high performing boats. Pitch is the theoretical forward distance, in inches, that a propeller travels during one revolution. Think of pitch as speed, or as the gear selection on a cars transmission.
Three or Four Blades
Pitch Vs 19 Pitch Prop
Again, we want to make sure that you are really understanding the foundational principles of propping your boat. The only way to determine the correct prop is through good ol trial and error.
Swapping and testing different props until you identify the sweet spot in relation to your RPM range and limiter setting.
Each engine has a specific top-end wide open throttle RPM range. Each engine manufactured in the last 20 years will also have the rev limiter .
If we put a small diameter prop on an engine with a low pitch. What will most likely happen is the power of the engine will overpower the ability of the propeller.
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The Meaning Of The Numbers On A Prop
Typically, most propellers will have specific information engraved on them. This information usually consists of two to four sets of numbers and letters.
One being the propeller diameter, the second being the pitch length, third representing the rotational direction and fourth being the bore/shaft diameter.
An example of these numbers displayed resembles the following: 15.6 x 15 | RH | 1 ¼
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Should You Go With A Different Pitch
All marine propellers involve a tradeoff. If you prop your boat to maximize top speed, acceleration will be compromised and visa-versa. Therefore, the first consideration is whether to optimize top speed, acceleration or some combination of the two.
To increase acceleration, consider reducing your pitch. This makes particular sense if you are NOT hitting the max RPM level established by the engine manufacturer when running at Wide Open Throttle with your current prop. To see the potential impact on top speed, enter your current values for Max RPMs, Gear Ratio, Pitch and Prop Slip in the Boat Prop Calculator tool. Then, decrease the pitch by an inch or two. However, as you do this, you should increase your RPMs by approximately 200 for each 1 reduction in pitch .
Conversely, to increase top speed, consider increasing your pitch. This is especially relevant if you ARE hitting the max RPM level established by the engine manufacturer with your current prop. However, it is hard to tell whether your RPM level is the best your engine can do or if it is being capped by the engines rev-limiter . If it is the later, then you likely have room to improve your top speed. If it is the former, then it might not make much difference after you account for the fact that each 1 increase in pitch will result in approximately a 200 decrease in RPMs.
The 7 Best Boat Propellers For 2021
by Ian ForteyUpdated on August 19, 2021.
Boat Safe is a community supported site. We may earn comission from links on this page, but we have confidence in all recommended products.
Buying a boat propeller seems like it should be an easy task. But there are actually so many factors you need to take into consideration. It can leave you scratching your head. Lets cut through the confusion and take a look at the best boat propellers on the market today.
The Quicksilver Black Diamond is the best all around boat prop youre going to find. Its not too expensive, but its built to last and to perform. In fact, its the best-selling aluminum prop in the world.
This is Quicksilvers 3 blade design. Its right hand and comes in a large range of pitch sizes. You can use this anywhere from 25 horsepower up to 250 horsepower outboard motors. Its also suitable for Alpha One sterndrives. It operates with the Flo-Torq hub system youll find on many outboards.
The included hub will work for engines up to 60 horsepower. If you have a bigger engine, you can pick up a different hub system to get the job done.
Once installed, expect to see a big improvement in planing. This model also offers a solid hole shot. That refers to your boats ability to accelerate. That means from a standstill or just low speed. If you hate slow acceleration, a good hole shot is important.
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What Problems Are You Looking To Solve
Is your boat sluggish coming out of the hole and slow to get on a plane? Are you not hitting the top speed you think you should? Do you want an improvement in fuel economy? Hoping for better all-around performance? Is your current prop blowing out or ventilating excessively in turns or when you accelerate? Are you looking to improve your boats watersports performance for tubing, skiing or wakeboarding? Once you have defined your goals, you can move on in the selection process.
Should You Pitch Up Or Pitch Down
Engine rpms and pitch are inversely related. Increasing the pitch will decrease engine rpms and decreasing the pitch will increase engine rpms. As a general rule, a two-inch increase in pitch will result in a reduction of 300 to 400 rpm. Conversely, a two-inch decrease in pitch will result in an increase of 300 to 400 rpm. Going back to the question of performance at WOT, if your engine is under revving, consider a propeller with less pitch. If your engine is over revving, consider a propeller with more pitch.
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Pros & Cons Of A 4 Or 3 Blade Prop
For us, if we go from a three blade to a four-blade without changing the diameter or pitch of the prop, we will lose top-end speed. What we will gain, however, is our hole shot .
Meaning we will be out of the water and cruising much quicker thanks to the extra blade generating a better grip from the prop to the water.
With the extra grip also comes better control and handling of our craft. Understanding these simple concepts is the crucial base foundation for us to begin the propping procedure to get the correct prop for your boat.
At the end of the day, it is ultimately up to you and what you are looking to get from your boat. Would you rather have a better hole shot or top-end speed?
Its your call! Personally, running larger boats close to the 30-foot range or higher calls for a 4 blade as its best for the size and weight of the boat. That extra blade really makes a notable difference in getting the boat out of the water and controlling it at higher speeds!