I am a freelance writer, author of 5 books, grant-writer, poet, river rat, amateur astronomer, and nonprofit consultant from Texas.
How to Pick the Right Propeller
Choosing the best propeller for your pontoon boat is not an exact science. If you don’t have the luxury of field-testing a variety of propellers, you will probably want to stick with the manufacturer’s original propeller style. Here is a list of the factors with which you can choose the best propeller for your pontoon-style boat that will help you do what you want to do with it.
Read the Label
Manufacturers label propellers by the diameter and then the pitch of the prop. These are the only standard marks provided on all propellers; other labeling is determined by the manufacturer.
A “13 x 16” propeller has a 13-inch diameter and 16-inch pitch. Your engine's manual will provide you with prop recommendations for your boat. Tweaking your boat’s propeller should begin from the manufacturer’s standard recommended prop.
Consider the Material
Aluminum propellers are the most common type used for pontoon boats. Stainless steel propellers are stronger, stiffer, and more efficient, and they may give you more satisfaction, but they do cost more. Older composite or plastic blades are useful as replacement props in an emergency, but I don't recommend them for everyday use.
Now some of the newer composite props from manufacturers like Pirana have begun to show performance numbers and durability equal to or better than their metal cousins. Prices vary, but the prop's construction material is the primary factor that determines the cost of all boat propellers.
Find Your Recommended RPM
Check your manual and find out what the recommended RPM (rotation per minute) range of your engine is at full throttle. Usually, this is between 800 and 1,000 RPMs.
When you select a prop, check first to see that the propeller operates within its rated RPMs with the throttle fully open in a straight line. If the prop makes the boat go slower or faster than this range, it isn’t right and you need to adjust one of the factors below.
Find Your Ideal Diameter Range
The diameter or width of the blade is a critical factor. An overly large blade can overtax a small engine and make it run slower, while a blade that's too small can cause the engine to spin too fast and damage it.
The weight, size, and normal cruising speed of your boat determine the diameter range that is ideal for your boat.
Factor in Pitch
The pitch is the angle of the blades. The number assigned to the pitch refers to the theoretical distance a specifically angled propeller will push forward through the water per rotation.
A 24-pitch prop will ideally push 24 inches through the water in one revolution of the blade. In practice, slippage makes it a bit less than that. Lowering the pitch of the prop gives the boat more power and better acceleration. A higher pitch makes the boat go faster at the top end, but needs more power to run within a safe RPM operating range.
If your full-throttle test shows the RPMs are too high, then you need more pitch. Therefore, if your RPMs are too low at full throttle, it means you need less pitch. Experiment by trying the next larger or smaller pitch and testing again. A one-inch pitch decrease will generally increase RPMs by 250 turns a minute. A one-inch pitch increase will decrease RPMs by 250 RPMs.
Decide on Your Ideal Number of Blades
For practical purposes, three- and four-blade props can be used interchangeably with most boats. It's a matter of preference more than anything.
The four-blade propeller, however, gives slightly more control at low speeds than the three-blade does at the same pitch. This is useful for steering a pontoon boat, which has a large profile. Surface winds can blow the boat around when docking or negotiating narrow spaces. A four-bladed prop helps provide you the control you need to safely dock in a breeze.
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You can also get the same level of control with a larger diameter three-bladed prop at lower pitch, but you’ll lose some speed on your top end.
Choose Your Blade Thickness
Individual blade design determines how thick the blades are. The rule of thumb is this: the thinner the blade, the less drag and the more efficient the blade. However, if you will be traveling in water with obstructions and obstacles, you may want to choose a prop with thicker blades for added strength.
Determine Your Optimal Cupping
Cupping is the curl at the trailing edge of the propeller used to give the prop a better grip on the water. Remember that if you increase or decrease the pitch of the prop you select, then you should also consider whether the cupping changes as well.
More cupping increases the propeller’s grab and increases stress on the engine, reducing RPMs. Less cupping will increase RPMs.
Calculate Your Slip
Slip is the difference between the theoretical movement of the prop through the water at the rated pitch and the actual performance. Typical propellers have a rated slippage of 10 to 30 percent. Slip numbers will impact pitch numbers.
A 24-pitch prop with a 30 percent slip rating equals an actual performance of 16.8 inches per revolution. A 22-pitch prop with only 10 percent slip numbers equals a 19.8, making the 22 pitch prop faster than the 24-pitch.
Determine Your Ideal Rake
Rake is the angle by which the propeller blade leans aft from the hub. Higher rake angles help high-performance boats reduce the loss of power due to air being pulled down from the surface between the turning blades. Lower-speed boats like pontoons use a lower rake-angle blade for better bite.
Questions & Answers
Question: I have a 2016 23 ft Avalon with a Yamaha 115 sho. The current prop is 13.5 diameter 12 pitch. At 4800 rpm the prop blows out and the rpm's go up to 6000, and the boat only goes 19mph. Would a larger diameter prop 14 eliminate the blowout?
Answer: It sounds like you need a prop with a little more bite to it. Talk to your boat dealer and the guys at the marina. They can advise you as to how to prevent blowout. Do you have a 2, 3, or 4 blade prop?
Question: l own an ss190 pontoon with 90hp, 16X12 turning 5200 rpm & 22 mph. I was told this set up should turn closer to 6000/25-30 which I will need for tubing purposes. What do I need to do to achieve this top rpm/mph? I'm a true boating rookie so please excuse if I don't understand the lingo.
Answer: The article explains how to pick a propeller that does what you want. If you want to do tubing you need speed, but with enough torque left to drag the tube around the lake. Spend some time with your marina parts guy - the one that sells the prop. He can give you the standard prop and advise you on alternatives you can order for more torque, more speed, or a combination of the two. You'll have to experiment a bit as the article above explains.
Question: I have a 2018 sun tracker with a mercury 90. I would like to get a little more speed. I have a 15.6 x 13p rh 3 blade prop; whats next best option for more speed?
Answer: Lowering the pitch of the prop gives the boat more power and better acceleration. A higher pitch makes the boat go faster at the top end, but needs more power to run within a safe RPM operating range. If your full throttle test shows the RPMs are too high, then you need more pitch. Therefore, if your RPMs are too low at full throttle, it means you need less pitch. Experiment by trying the next larger or smaller pitch and testing again. A one inch pitch decrease will generally increase RPMs by 250 turns a minute. A one inch pitch increase will decrease RPMs by 250 RPMs. For practical purposes, three- and four-blade props can be used interchangeably with most boats. It's a matter or preference more than anything. The four-blade propeller, however, gives slightly more control at low speeds than the three-blade does at the same pitch. This is useful for steering a pontoon boat, which has a large profile. Surface winds can blow the boat around when docking or negotiating narrow spaces. A four-bladed prop helps provide you the control you need to safely dock in a breeze. You can also get the same level of control with a larger diameter three-bladed prop at lower pitch, but you’ll lose some speed on your top end.
Question: I have a 25’ pontoon with a Yamaha 115 4 stroke, will a 4 blade prop give me more control to get it on my bunk shore station?
Answer: A 4-blade prop may run smoother and reduce vibrations as it is balanced around 4 points as opposed to 2 or 3. A 4 blade is a great choice for heavier boats. The increased blade area can power the boat more efficiently. If the size of the prop is limited, a 4-blade prop may allow for a more efficient pitch. If you run at better than 1500 rpm, a 4 blade will smooth out vibrations. Also if the boat has limited horsepower, a 4-blade can give you much needed blade area to give the boat more torque.
Question: How do I determine if my outboard is hanging too low on my pontoon?
Answer: There are so many kinds of hull shapes, you really need to have someone at your marina or boat dealer take a look at it. Every boat is different. Mainly it's about finding what works best. It's a process.
Question: I have a 22ft two tube 25" tubes pontoon. Weight is 2000 without gas and motor. I have a Suzuki 140hp four-stroke. My top speed is 23mph at 5200 rpm. Max RPM IS 6200. Running 17 pitch aluminum 3 blade prop. Is there any hope?
Answer: You might improve performance by changing the prop. It depends on what you are looking to do. If you are wanting more speed you can do that, but you'll likely sacrifice the bite you get. I've seen boats that were fast but bogged down if you put a skier behind them. The top end was better but the boat was slower off the start. It's a compromise in the long run between power and speed. You have to decide what you want. A pontoon boat is not exactly designed for great speed. In the South we call 'em party barges, not exactly a name that invokes the image of speed. The article above shows how to test to find a prop that does what you want. There is unfortunately, no prop that improves both speed and power for the most part, unless you have a tiny little prop more suitable for a trolling motor. That's the only situation where I think you can improve both.
Unless your motor needs some work, changing your prop will be a trade-off.
Question: I have a 1996 Yamaha T50 pontoon series on a 20ft Bennington. What is the best pitch? And, can I use a 4 blade instead of 3?
Answer: It depends on whether they make a 4 blade prop that fits your particular boat. Read the article above and do the steps. Decide what you want, speed or torque. If you're carrying a lot of weight or trying to pull skiers, you'll want a prop that will pull a load. If you want to buzz about at high speed choose a pitch that gets you that. The "best" pitch is the pitch that helps your boat best do what you want it to.
Question: For my 18-foot pontoon with 60hp Mariner, is there a best all-around propeller?
Answer: Pick something between high torque and high speed. It's strictly up to you as to how you want it to feel out on the water.
Question: I have a 1999 Bennington 2275 RL Pontoon with a 90 HP Honda outboard. It would only go 12-24 MPH @ 4800 RPM top speed. I re-proped it with a Solas 13 3/4 x 13 stainless and picked up low-end turquoise and top out now at 21 MPH @ 5400 RPM. Is there any hope for me to gain any more speed with a different propellor on my pontoon boat?
Answer: There might be. A boat that size though is going to strain a 90 hp motor. At summer camp when I was waterfront director we had a 90 horse outboard ski boat and with my big butt and low center of gravity, I could lay back on the skis and just about stall that poor thing. If you want more speed, you could get it, but at the cost of a long buildup to top speed and a commensurate loss of torque. If you want speed, get a bigger engine if the boat can handle the weight and power. Check with the manufacturer. Also, your hull design might also limit your speed. Do some research. You may find some good suggestions from other owners of your model boat.
Question: I have a 24ft. pontoon with 115hp 2-stroke. What’s the best prop size for the best gas mileage?
Answer: There's no way for me to answer your question about your boat. You have to spend a little time and effort to determine which propeller will perform the best for your boat.
You need to do three things to answer this question: (1) Read the article and make notes so you understand what the guy at the boat parts place is talking about. (2) Read the part of your boat's manual which tells you about your motor's rating, the recommended propeller diameter, pitch, and slip. And (3) visit the parts store and tell the parts guy whether you are looking for more speed, more torque, more durability, or more maneuverability.
Those four factors and what you learn from your boat's manual will help you and the parts guy determine the diameter of the prop, the pitch, and the effect of slippage of any given prop.
Question: I have a 1995 Mariner 60hp with an 18-foot pontoon boat. What propeller do I want?
Answer: You want the propeller that best does what you do most. If you pull skiers, you likely want more torque so they pop out of the water. If you're all about the speed, then go for one that gives you speed.
Question: I have an older 24ft. pontoon boat with a 70 h Mercury Force. What size propeller would you recommend?
Answer: Like the article says, it depends on what you want to do with it. You can go with slow and more powerful, or fast and more easily bogged down (if you are towing a skier for instance. The article explains how to determine what sized propeller you need. The easiest way is to talk to the guy at the marina. If he has any technical experience he can walk you through the options.
Question: I have a 115 e-tech on a 20 ft Sylvan pontoon. What propeller do I need?
Answer: It depends whether you're going for power or speed. Decide that first and then follow the instructions laid out in the article to determine the pitch of your prop. Your local marina guys can probably help you or the boat dealer you buy your props from. Do the tests recommended above so that you'll go in with a better understanding of what you want.
Question: I have a 2013 Bentley 24-foot Pontoon with a 115-horsepower Mercedes four-stroke engine. It has a four-blade prop on it. It revs high and goes slow. What would be a good propeller for this boat?
Answer: Check the article. I can't tell you what an ideal prop for you would be. It's a personal preference. The article helps you adjust the prop to get more speed or more torque. Work with the parts guy. He can help you get the prop that will do what you want it to.
Question: I have a 20ft Kennedy Pontoon, and a 50hp propeller. What would be the best propeller to pull a tube, and potentially a water skier?
Answer: Experiment with the propeller as described in the article. Talk to your parts supplier. There's no pat answer. Every hull type, engine size, prop pitch, shape, weight and upper profile of the boat will make a difference. I've given you a method of experimentally determining the most efficient prop for what you want to do with your boat.
Question: If you have a 24-foot pontoon with 85 HP, V-4 engine what size propellor is best?
Answer: What's best is based on what you need. You need to spend some quality time with your boat parts guys and explain to him what you need for the boat. The best prop depends on engine size, hull configuration, and what you plan to do with it. Consider if you need speed, torque or a balance between the two.
Question: I have a 22’ Crest Pontoon with large toons and a 90 hp Yamaha, I have tried 14x11 and 13.5x13 and they both turn 6000 RPMS, what do we need?
Answer: Talk to your supplier. Tell him you are looking for (I assume) more bite on the prop. He will recommend a blade that will do that for you.
Question: I have a 21-foot Pontoon boat rated for twelve people, and powered by a 1997 Johnson 50HP 2 Stroke motor. What is the best aluminum propr for this boat?
Answer: It depends on what you want to do with it; speed or power? That's your choice. Follow the suggestions for testing in the article to fine tune it. It's all a matter of whether you are getting the performance you want out of the prop. If you find yourself bogging down, you need to go for a prop with more power, but you sacrifice speed. If you want to go faster and don't load your boat down with a lot of people very often, you can go for a higher speed prop as described above. Every boat has it's own characteristics depending on hull shape, engines and the load it's carrying. You do have to do the testing bit. There's no off-the-top-of-your-head answer. It depends on your boat and what you want to do with it. Boats are like wives. You have to learn their idiosyncrasies if you want to get along with them.
Question: I have a 22-ft. tritoon with a 140 hp Suzuki engine. What kind of prop do I need?
Answer: The prop you choose will depend on how you use the boat. Do you want speed, power or something in between? Talk to the guy at your marina and perform the checks recommended in the article. If you just want a standard prop, ask the guy at the boat supply. If you're going to tweak it more to your liking, try the suggestions in the article.
Question: I have a 100hp Johnson on a 20-foot pontoon. What prop do I need?
Answer: Again, all I can tell you is to go through the steps in the article and make some decisions about what you want. If you need power, you will choose a prop with more torque to it, but you sacrifice top end speed. If you want speed, you select a prop that will give you speed, but you sacrifice pulling power. It's up to you. Do the things recommended in the article and then talk to the guys at the marina. They'll help you pick a prop that does what you want it to.
Question: I presently have a Solas 15 inch with 15 pitch 3 blade propeller (9512-150-15) on my tritoon. The prop performs well with a max RPM of 5700 or with 3 people 5400 RPM. My engine is a long shaft with an LH rotation propeller. Should I leave well enough alone or go to another propeller?
Answer: If it's working for you, you might not want to change it. If you need more speed or more torque see the article above.
Question: I have a 21 Foot Pontoon boat, rated for 12 people. It is powered by a Johson 50 hp 2 stroke motor (1997). What would be the best prop?
Answer: I can't say. The article tells you how to figure that out. Once you know whether you want speed or power or some balance between the two, then you can talk with your marina guy, and he can help hook you up.
Question: I have a 22' lowe pontoon, a 115 proxs with a black diamond quicksilver 3 blade propellor. Sometimes on rough water at high rpm, or if I trim up a little, I lose my bite on the water and also when pulling a tube. How can I keep my pontoon from bouncing at high speeds?
Answer: If you are bouncing along in rough water at high speed, the hull shape of a pontoon boat doesn't lend itself to sticking the prop down in the water. It's going to bounce high, go shallow and cavitate. Now pulling a tube and having the prop slip suggests you need a prop with higher torque for more pulling power. You will sacrifice top end speed for torque though. You have to decide whether you want to go fast mostly or pull tubes and skis.
Question: I have 23’ 2019 tritoon lowe With 150ph engine on Lake Tahoe (6,224’) what kind of prop should I have?
Answer: I can't tell you that. It depends on what you want to do with it. It's a process. Work with your marina and do the things described in the article. It's a partnership between you and your supplier. Talk about whether you want more power (torque) or more speed versus what you are getting now.
Question: I have a 23 ft. Caravelle Razor with a 200 Suzuki and a 19 pitch propellor. Where should I be with it?
Answer: On the lake! If you don't like how it feels then get a higher or lower pitch depending on whether you want speed or power or some combination of both. The guy at the marina can help you if you can tell him what you want. If it feels sluggish, then tell him you want more torque. If it feels slow, tell him you want a faster prop. It depends on what you want from the boat.
Question: I'm looking for a specific opinion on a prop for my 60 mariner pontoon boat; generic answers are all over the web. Do you have any specific product recommendations?
Answer: I'm not sure on brands. Your best bet is someone who works in the parts department of a local marina before you go to the boat store. He might have some opinions on what are the best brands. You can use the pitch and size of your original and just alter the material it's made of or the number of blades. If you want to get jiggy with it, follow the suggestions in the article for tweaking it.
Here are five top brands of props for 2018 from the Marine Lab website:
Turning Point Aluminum, 4 blades
Turning Point 31501931 Stainless Steel 4 blades
Quicksilver Nemesis Aluminum 4 blades
Mercury Black Max 3 Aluminum 3 blades
MotorGuide Machette III Aluminum 3 blades
Question: I have a 24 ft Bennington with 300 hp Volvo penta, looking for a stainless prop just curious what you would suggest?
Answer: Really there's no substitute for putting your butt in the seat and running her around the lake to see how she handles. If you don't like how she handles, then you have to pick a solution and adjust your prop accordingly (see the article for details). If she's sluggish, you may need more torque. Your marina can talk to you about how to change to a prop with a different pitch. If you have a need for speed, then you'll want a prop that gives you more speed. There are other issues like cost, durability, blade width and the size of the engine that will be pushing this beast. Sounds like you have plenty of power. It's just a matter of deciding what you want to do with that power. If you'll be pulling skiers, you might want more torque to offset the drag. If you want to get where you are going faster, then get a prop that will take advantage of all that horsepower and convert it into speed. And you may want to test different props to find one that makes you happy. You might even keep a high torque and high-speed propeller and swap them out depending on what you are going to do on your afternoon on the water.
Question: I have a 1996 24’ pontoon with a force 120 on it. What would be the right propeller for my pontoon boat?
Answer: Mostly, I would suggest you go through the steps outlined above. There aren't really any shortcuts. There's no substitute for putting your butt in the driver's seat and testing how she handles. Once you know what you've got and what's missing, you can work through the steps in the article and have an intelligent dialogue with your marina guy and start looking for just the right prop.
Question: I have a 25 ft pontoon boat with a 90hp 2 stroke engine,what would be the best prop?
Answer: I can't tell you that. It depends on your hull shape, the width of your boat, the weight of your boat and the condition of your engine. It's really a matter of testing. The principles in the article will give you a method for determining what will work best. You start with what you want to do with your boat. If you need torque for pulling skiers or speed for cruising or maneuverability for working around those good fishing holes. The article and your marina guy can tell you how to increase speed, power or maneuverability.
Question: A 1977 Harris flotebote 24-ft with a 120 inboard what prop should I be using?
Answer: Start with the manufacturer's recommended prop. If you don't like it, talk to the marina parts guy and tell him whether you want more speed at the top end or more power at the low end. It's up to what you want. With some experimentation as described in the article, eventually, you'll settle on a perfect prop.
Question: I have a 28ft pontoon boat with a GM 4cyl motor with 140hp, I have a Mercruiser Alpha 1 lower unit, what would be the ideal prop for all-round good operation?
Answer: As I said above, that all depends on what you want to do with it and what you mean by "all-around". Your all-around and my all-around are probably two different things. If you want more speed than what you're getting, tell the guy at the marina parts place. If you want more torque and power, tell him that. He can help you adjust the size and pitch of your new prop to give you the performance you are looking for.
© 2010 twayneking
twayneking (author) from Puyallup, WA on April 07, 2021:
If you want more, you could always tweak your engine. With the prop changes you either get more power and less speed or more speed and less power. Depends on what you're doing with the boat.
twayneking (author) from Puyallup, WA on April 07, 2021:
That may be all you can get. It's a trade-off between speed and power. You either get more speed and less power or more power and less speed. You have to decide which you'd rather have.
twayneking (author) from Puyallup, WA on April 07, 2021:
Sorry. You'd have to check with your marina or boat dealer.
Roger w on August 18, 2020:
I changed the motor on my pontoon boat to a bigger one I was told it needs a bigger prop any suggestions on which one I should use it’s a 1988 force 85 horse 20 foot pontoon
Jeffery Blye on August 16, 2020:
2017 starcraft MX23L HMX Tritoon with a Yamaha F200XB Currently running a quicksilver 16x13p getting 30mph @ 5000rPm WOT it feels like I should be getting more Range for motor is 5000-6000 rpm just purchased from a private owner Any help appreciated
Kimberly Fife on July 11, 2020:
What prop should I get for 2002 Yamaha Outboard 80hp [ F80TLRA]? I have a 2002 SunCatcher G3 pontoon boat. 22' long.
Kimberly Fife on July 11, 2020:
I have a 2002 SunCatcher G3 3pontoon. It's 22' long.
keith on July 07, 2020:
I have a 20dlx suntracker 90hp fourstroke command thrust it came with a 15p three blade aluminum prop. I purchased a 15p four blade stainless haven't run it yet but everyone I talk to thinks this will be to much prop?
walkerdanny on May 31, 2020:
Hello all we just bought a 2020 sun tracker 22’ dlx pontoon. Ordered the top of the line 115 pro xs command thrust Mercury tracker states that boat with that engine should see speeds up to 28 mph. Boat came with a 16-13 prop. Only saw 20 mph at 5000 rpm. Mercury says we should be seeing 6000 rpm. Tried 2 other props. 16-11, we were seeing 6000 rpm but only 21 mph. Tried a 16-12 and are getting 6000 rpm and a whopping 21 mph. This sucks. We are at 3000 ft elevation. Are all the manufacturers exaggerating on the top speed like car dealers do on mpg? Is this the fastest I can go?
hal dunn on April 10, 2020:
I have a 20 ft cypress cay with 90 hp mercury 4 stroke (2008) looking to put a new prop on,doesnt give size on prop,only pt.no.77142a45p15.
can you decipher ?
twayneking (author) from Puyallup, WA on December 05, 2019:
If the boat came with a prop on it, that's your starting place. Talk to the guy at the marina. He can probably tell you what prop that boat came with. This article is about tweaking your prop's size and pitch to suit your needs. There's no perfect prop. Only what's perfect for you. - Tom
mr. brown on December 05, 2019:
need a starting accurate estimate of what pitch to put on a
4 stroke yamaha on a 2 toon 24foot Bennington SL
I want to run a Yamaha Talon Aluminum 13.5 but not sure which pitch
twayneking (author) from Puyallup, WA on September 28, 2019:
I apologize for not answering all your questions. Many of these questions concern what is the "best" prop for your own individual boat. Having attempted to answer such questions honestly, the editors of this site have rejected my answers to these sorts of conditions because I keep referring back to the article. There is no perfect prop for a boat. There is only the perfect prop for what you want to do with the boat. I've given you principles for figuring out how to find the prop that works best for you. Finding the perfect prop is an experimental process. As with all boats and wives, you have to find the sweet spot where they do what you want them to do.
philbert on August 09, 2019:
does the wrong propeller cause cavitation?
Old Dad on September 19, 2017:
I have a 21 foot Sweet Water pontoon boat with a 50 Hp Yamaha 2 stroke, 12 1/4 x 9 prop. At full throttle it operates at 4,200 rpm and about 21 mph with 2 persons aboard. Is this normal or should the rpm be higher.
OldTimer on August 08, 2017:
I have a 2003 Bennington 207 SIC. Lifting strakes and larger logs with a 90 hp Merc. Very interested in the pontoon water glide experience or if anyone is willing to part with.
twayneking on July 28, 2016:
Read the article as a starting point, then take what you have learned to a marina and talk about it with the technicians. They can probably take what you tell them and make recommendations as to how best to solve your problem.
Keith on July 27, 2016:
Hi have a 24 ' TMC Pontoon with a 70 HP Evinrude 2 Stroke 3 Cylinder motor . I am looking for the right size prop. Does anyone have a good idea ?
pondboy on September 20, 2014:
My 24 Toon we just installed a water Glide and now cant find the right prop and the glide people are not much help after its installed as it seems you just have to spend a lot on props to experience the a lot of hooey and hype about the glide. Putting it on E bay and leaving boat stock as the manufacture made it..
Tom Schumacher from Huntington Beach, CA on February 14, 2013:
Good hub. Most people don't understand the nuances of prop design, such as cupping, slip, and rake. Your write up was interesting and informative. Thanks for sharing.
twayneking (author) from Puyallup, WA on March 09, 2012:
The starting point is the prop you've got. Test it on the water and figure out what's off. First check the max rpms for which the engine is rated in the manual. Then do the full throttle test described to see whether the full out rpms are too high or low. Too high, increase the blade diameter or increase the blade pitch. Too low? Try a smaller prop or reduce the blade pitch to increase the rpms. Talk to other owners of your boat and engine and find out what other factors impact performance with your boat and engine. Try adjusting the rake of the propellor or change the composition of the blade. It's not an exact science. There is lots of tweaking involved to get a boat to do what you want it to. - Tom
eric.d on March 08, 2012:
I have a 21' pontoon that now has a 3 blade 14x11 with a 115 mercury prop doesn t seem right . I have not been out much yet and am looking for a starting point or advise for right prop