Upgrade Your Trolling Motor for $4 [Airplane Prop on a Trolling Motor] 

A towel draped across the opening in the hull would be good insurance against dropping a nut into the water.

More thorough than most of the videos I've seen regarding prop swaps. Like the data & graphs you provided. You may have saved me a lot of time & effort on my canoe setup.

Hey, Tyler, love the video! Great stuff. I am both an engineer and model airplane pilot, so will hit a couple questions you raise. Causes: There are likely 2 causes of increased speed: better foil shape and less drag. The air prop is "skinny" and appears to be about as thick as the water prop. This makes the share that moves through the water more like an airplane wing and less like a sheet of paper, which gives more thrust for the same rpm and less drag as well. Also helping out a lot, drag increases with area, so "skinny" is good, and makes the shape improvement even better. Complication: I have no idea what that motor controller is doing. If #7 means 70% of available volts, then the lower drag will mean rpm increases, making even more thrust. Otoh, if #7 means 70% of max rpm, then amp draw will be less due to lower drag, and thrust slightly increased due to better shape. This detail isn't clear. More complicated: hull drag increases exponentially with speed, after a point. It's not surprising that at high speed the graphs converge - that's the boat getting difficult to drive thru the water. One nit pick: the correct estimation of potential range is speed vs amps. A 10% increase there will result in a 10% range increase, because...math :) When you get 10% more speed at a throttle setting, but the motor is drawing 10% more amps, range is unchanged. It's much more informative to collapse the two charts into one, getting rid of the "speed setting" factor and plot each setting's amps against its speed. Down sides: these props won't flex much with impact. Hopefully they shatter before bending the shaft. Also I expect them to be very easily clogged by weeds. Other comments: I haven't handled the water prop, but I bet it's much less stiff than the fiberglass reinforced plastic used in the air prop. Those typically are very stiff, and fail when they hit something. They will hold shape better at higher rpms. Also, prop weight has zero to with motor rpm once at speed, and very very little impact on acceleration. Ideas to improve: 1. Maximize the prop length for efficiency. The longer the better, and clip the least possible off the tips. 2. Play around with pitch. It's a matter of changing props and seeing what works. Be careful of big pitch #s - you risk overheating your motor. Use your speed vs amp draw chart to compare. 3. Try out a spinner. That big flat face at the back of the prop is huge drag. Airplanes seldom run naked props because of drag at higher speeds. Water is a lot like high speed air. Back to the hobby shop for a spinner of about the same size as the old prop hub. Test again with speed vs amps and see if it helps. (Spinners are a pain, so better be worth it. May not be a good option for on the water prop replacement.) That was long, but skipped details. Happy to answer more questions.

more thrust is produced at the tips as they have a higher speed (longer prop = higher tip speed), less pitch = higher rpm = more thrust at higher speeds. More pitch produces more torque hence faster acceleration (probably not necessary in a kayak, unless adverse wind/ current or heavier load). Hope that helps.

Well that was a " proper " test sir haha , just got my 3 rc props in the mail today . I'm exited about that mid range as most of my use is mid range power levels. One thing to note for anyone reading this is these rc props feel very sturdy / strong in ur hand , when u look at a pic or a vid they look very flimsy / cheap but after getting mine today I can assure u they feel strong / great in person . They feel like a 15 dollar prop in ur hand not a 4 dollar prop if that makes sense. Thanks for the vid man , big " props " to all ur effort haha

Great info. The graph and performance results are very helpful🤙

This might be a better fit for transom or bow mount motors. I saw the same video you are replicating and it's really good to have the verification. The airplane blade is NOT at all weed free, and it's probably smart to carry your original prop in case of a problem. Thanks man!

Just a note from a RC airplane nut, Get a cheap prop balancer when you trim the prop. Winn be more efficient and your motor bearings will thank you . Great movies Thanks

We need to link up so you can show us some tricks for setting ours up! We’re excited to get into some kayak fishing.

Holy crap, that's an amazing kayak setup.

This is cool! For that price I gotta try it. Ordered the prop

Great test and discussion

Great job Tyler!

I just ordered the ACP prop for my trolling motor. They had an entire category on their website for trolling motor props. Several options and styles to choose from. What I will say is that… the aircraft prop looks a LOT like the prop on my old pedal drive kayak. It lasted a great many trips and bumps into oyster/sand bars and mud flats. Just don’t put it into reverse when in the muck! The blades are thin on the backside and that is when they get damaged. The only thing I ever had wrapped around that prop was about 150ft of 30 lb braided line one time that I snagged in the open ocean. Good thing I had a knife on me or I would have had to paddle back. The seedless wedge design would not have made a difference for me on that one. I may go back and buy a few different designs from them to see what is the most efficient.

Just ordered my props. Also tried a 10-8 LH prop. Thanks

Prop twist has a lot to due with efficiencies and speed and needs to be matched to the rpm of the motor for peak efficiency. I believe the reason the rc prop is increasing the speed is because it matches the rpm of the motor and density of water as well a having less surface area and a larger usable thrust area with the small hub. That's just lucky that this prop matches the motor well in water, a different propeller may be better or worse. Mostly I think the reason is the increased drag on the propeller is the main factor, the stock propeller is just so much bigger when it comes to area coverage and that causes drag.

I just finished installing one of these props on my Minn Kota Endura 55 Max(it weighs 26lbs). The installation was slightly different than shown on yours as the hub is slightly longer, so I had to add 3 3/8 flat washers,and one 3/8 lock washer. I have a Lifetime Tamarack Angler 10ft. fishing kayak(49 lbs,maximum carry weight 275lbs )that I motorized as a "science experiment" ! I've been running it with an Everstart Group 27 deep cycle battery(48lbs,110AH)battery. The motor mounts on a homemade transom made from pvc plastic pipes ,and fittings, for the frame. The transom itself is made from a 3/4 in thick pine board that was sealed and painted. I've added a 6x6x1 nylon block to mount the motor on the board. All in all, it's a fairly sturdy set up! I did have to add a set of stabilizers to not only stabilize the craft, but to also increase the weight that it can support, due to the fact that with myself and everything aboard it's slightly overloaded! I just ordered my very first lithium 100ah battery that weighs only 25lbs,and that loss of 23 pounds should help! My maximum speed before adding the stabilizers was just under3mph(2.94mph). Adding the stabilizers dropped it a little bit down to around 2.5-2.75 mph. I'm hoping that adding the 10-4 propeller will increase my top end speed, and possibly increase the range as well. I'll let you know how it does!

The aircraft prop has a higher aspect ratio than the boat prop, making it more efficient. (Think high performance glider versus a biplane) . This is due to less energy being lost to tip vortices with the higher aspect design. More simply, the boat prop is working like a screw and the airplane prop more like a wing. It has absolutely nothing to do with weight or rotational momentum. The limiting factor for the aero design will ultimately be cavitation on the upper surface of the blade, but for low speed operation like this it probably should be fine.

I think you nailed it with the smaller hub. More prop length at a cost of less durable.

Tried whole bunch of props in different sizes and pitches. Not much of improvement, but larger ones just draw more current. Ended up leaving stock prop and added PWM controller and amp meter. For my Minn Kota C2 50 the best cruise speed at around 26-28 A. If I crank all the way up it draws 40A with tiny gain in speed.

It works better than stock. But get clogged very easy with weeds etc

Nice. Running a trolling motor off the back doesn’t have the problem you have with regards to the prop hitting and might gain speed.

pretty cool video

Great video for sure. I think it’s mostly rpm. With either prop you are going to max out at some rpm for each. Could you spin the oem prop faster obviously you get more speed up to a point where flex and cavitation comes into play. I suspect that skinny little prop would reach its maximum effect speed and failure long before the oem prop does. That little trolling motor is only going to spin so fast. Make it spin faster it’ll go faster. To a point I guess. I believe a three blade prop will actually get you to max speed faster but I don’t think on the same motor it would go any faster with 3blades. Most trolling motors are two blades to better chop up the weeds.

Props for aircraft have a higher pitch do to air being thinner than water. At low speed I don't think you're going to have any problems but at higher speeds you're going to run into a few. Idk the math but you're definitely putting more stress on the motor because of the higher pitch u get more resistance. Another is in water cavitation is a factor u have to consider. A prop made for the water is designed to minimize cavitation a prop designed for aircraft doesn't have to worry as much about it

I saw the suggestion about using model airplane props on trolling motors long ago too and appreciated your in-depth analysis. I'm glad that you also measured the current draw of the props at different power settings. I had wondered if steeper pitched props might overload the the electric motors and result in excessive current loads at higher power settings. One issue about thrust is that I believe that it may diminish at higher speeds when the same power setting is constant. I suspect that the thrust ratings of trolling motors are measured when the test platform is not moving. I think this may be when the thrust would be greatest. Now I'm wondering about the potential speeds and current draw when using steeper pitches and where possible, longer propellors. Thanks for an excellent, thought provoking video!

I think the diffence is the amount of drag. I'd be interested to see if there is any change if you used a regular hex nut to secure the prop instead of the wing nut

Still watching but don’t forget the kill switch also acts as a wrench for the prop nut. 👍🏼

Thanks for the graphs, im a numbers guy and thats what i needed from this video. I assume it is possible but have any tech lords put a prop into a 3d scanner, tell the program to add 1-99% more pitch/size/thickness etc, print one at every 10% difference, run your exact same tests with each one. Find the sweet spot. Print 10 more 1% either side of that sweet spot, numerically. So on and so forth until you have the best design based on real world tests. Mass produce and sell on ebay. Hobby paid for itself.

The airplane prop is more efficient, but trolling motor props are also designed to go through weeds without getting them all caught up in the prop. So, if you are not in weedy water, it shouldn’t be a problem.

Hopefully going to try my hand at modifying this to be slightly more efficient.

What’s the weight difference between the two. The lightest one should move faster in my opinion, thanks. I saw where some people are waiting weeks for a replacement blade from Minn Kota as they are backordered. Just carry more spare blades for backup. Great videos, thanks

Great video. airline pilot here, and this video was really intriguing. I'm often wrong but I was thinking about something. You talked about having to trim the prop to clear the hull during rotation. I wonder, if it's just BARELY clearing the hull, I would think there might be some inefficient disturbance in the water flow with such little clearance between prop tips and the hull. I wonder if you trim just a little bit more, which would be counter-intuitive due to reducing prop length, if that would create less buffet in the water flow, and end up being more efficient. ?? I really have no idea, but just a random thought. Great videos, and I still haven't figured out if I want to splurge yet, or save for a real boat. :) best of luck!

I posted a video of testing various props on my Intex mariner 4 inflatable boat. I went from 3.7 to 4.3 using the 10X5m-LH prop, I believe you will gain more as well if you went with it

The original propeller is a single-turn wood helical screw. Two boats raced each other. One of the racer's screw propellers had a portion of the helical screw break-off. That boat suddenly sped up and won. The lesson learned is that surface drag is important. I am going to try two counter-rotating propellers. The reason is that I am going to see what happens when both propeller motors are out of the water, for less drag. only the bottom of each propeller will be in the water. Also, the motor mast will be out of the water too. I am thinking that design will have drastic improvements in efficiency. One worry is the bending moment on the motor and the fatigue from the propeller blades flexing. Rick Gellert

Hello, Tyler I really appreciate the quality and highly informative content you put out as well as being very entertaining! Great job! As a new kayak fishermen I have been watching your videos as I rig my new Old Town AutoPilot 120. I absolutely love trolling for walleye and musky from my new fishing machine. I'll be taking it out for salmon and trout soon. Quick question.... are you still having good results with the model airplane prop on your AP 120 and do you recommend others do the same to gain a little more speed? Also, do you still see the increased efficiency on the battery? Thanks!

The problem is not only the speed , you have to check the heat from the motor , the prop is calculated and fits the motor , you can always make it run faster.... and the original prop is ment to be a weed buster

own ap 136 ,not enough gain of sped vs weed edge benefit for prop change , saw comment once on you tube that "as per old town the speed is limited by the hull design and changing the thrust by prop or 55 lbs thrust motor would have little effect" , small outboard may be the only option for speed gain but liability issues are concern to all, explains why there only one side steel reinforced mounting place on the back of the AP instead of two .....

In my uneducated opinion it there is less mass with the smaller prop therefore less drag that results in the motor being more efficient. One thing I did notice and you may want to keep an eye on is the pin. With the original prop the pin is captured within the prop but with the small airplane prop the pin is only held in place with with friction or pressure from tightening the nut. Its open to both side and may eventually slip out. Just a thought.

I’ll pick up a couple if only for emergency replacement.

Surface area/volume. The rc prop displaces less water and also creates less friction. Top speed probably more limited by boat design and the prop -I suspect- begins to deflect under increased load and/or cavitation increases = less for blades to push on.

I’d say the extra speed is due to the smaller surface area cause less friction/resistance with the water.

You should try it again while dragging a tyre, see how it affects torque.

Interesting. I’d be curious to know how much that airplane prop is flexing under water while running at high speed and if it could endure the stress long term. And then how would an aluminum prop perform if it wasn’t flexing at all and holding its original form.

Consider "Laminar Flow Characteristics on Surfaces", and that might give you a better understanding on why the heck you're getting better speed vs. power draw. (Been using APC Props for a long time on my R/C Planes, and getting better speeds vs. amp draw, too! Batts. last longer, and I get to fly MORE!). Lol

My experience is in the world of aircraft. Real ones, not RC. And I have quite a bit of experience with aircraft props. RC aircraft or real aircraft, aerodynamics still work the same way. And hydrodynamics and aerodynamics are very similar in a lot of ways. That being said, you may be onto something when you spoke about the hub. Also is the cross sectional shape of the blade itself. The original prop blades are pretty much flat, and get their thrust from the pitch of the blades. While the airplane prop does this it has something else going for it too. Its cross sectional shape is like that of an aircraft wing, more curve on top than on bottom. This increases thrust in air and water. (Bernoulli’s principal) My other theory is speed. The airplane prop has less mass therefore the motor can turn it faster. My only concern with that is how it might effect the life of your motor if you’re constantly over speeding it? It’s probably marginal and not much of a concern, but something to think about. Cool vid man keep it up!

My bet is that the trolling motor prop was designed to work with a wider range of boat sizes with a more generalist application. The plane prop is probably better at higher speed with lower torque requirements. With a heavier (not necessarily longer) boat, the plane prop might lose performance. On the idea around why the plane prop works better for this boat is that it has a lower pitch and surface area. That allows it to spin faster. Think more rpms with less torque. What would be interesting would be to measure the rpms of both props in water to see if that's the case. How you'd measure that would take some serious thinking.

I'm also curious if the airplane prop will have any affect on your fishing success rates. As you have mentioned many times, Kokanee are sensative to motor noise in the water. I also wonder if cavitation at the prop is part of that issue. It might not be a low speeds, I don't know. Since you are gaining speed are you also putting more noise into the water, therefore spooking more fish than before?

“I don’t run into things” 😂 yeah none of us do until we run into something 🤦‍♂️😂 But for $4 dollars you can carry several spares for insurance as well as the original prop and it looks pretty simple to swap out.

I'd rather have the 4 dollar prop break and put a new one on. The oem props seem very unbalanced . I think I'm gonna get a few of the airplane props. The 10 percent range increase sounds good. Lithium and airplane props, what will i do to the boat next?

After working with model aircraft props, which are usually glass filled for rigidity. I can tell you that they will cause significant damage to flesh whereas most trolling motor factory props appear to be safer to fingers and flesh. Just a thought

Wow where is this? I’ve never been on a lake so calm and flat! It’s amazing looking.

It depends on what the prop pitch is too.

I’d be very curious about the ability to handle wind and chop using the airplane blade. With a smaller blade width, would there be enough water displaced , and thus force generated to counter a headwind.

What about coating the bottom of the hull with a hydrophobic material? Some kind of spray on stuff that adheres to the plastic quite well so you dont have to reapply the stuff.

I remember reading about Dick Rutan and the 76 Voyager, the first aircraft to fly around the world without stopping or refueling. They initially chose wooden propellers to save weight, but subsequent testing revealed that the greater efficiency of more rigid steel propellers more than made up for the greater weight, although it wasn't obvious, timber propellers flex and deform to an extent that it seriously affects their performance. I wonder if this might also explain the difference in efficiency here, with the model airplane prop being a lot more rigid?

If I were to guess the increase comes from the airplane propeller you have less weight and less drag so because of that you get an increase prop spin speed or faster rotation making it more efficient. the hub being missing I suspect is offset by the smaller overall surface area of the airplane propeller. Trolling motors were designed for full sized boats so the larger prop is basically forcing them to run in low gear so you have the power to push a larger boat. OK that's my guess we would need to have a bunch of different props to experiment to get a better idea to get to the bottom of it. I would like to see a hub added to the airplane prop see how that affects it.

Might make a good backup prop. probably fits in the tackle box. Who knows, props break

I got a bucket full of this propellers , in Plastic and in wood , so i will test them

Put on a prop nut cover and check vs n nut cover. I think that and pitch was the difference.

Very interesting experiment.....when we want more speed from an r/c plane world we go smaller diameter and higher pitch, and of course opposite for more thrust with lower speed. Might be interesting to change from the 10-4 and try a 9-6....

I'd be curious to see how this performs with a larger boat. My trolling motor is undersized for my boat so I'd be curious to see if this was an upgrade or as I one guy mentioned below, it might not have the torque to improve the performance with a bigger load.

Model aircraft props can be ordered with different pitch. A typical description on an aircraft prop is 10-6. The first number is diameter ( inches ) the second number is pitch. In this example... the 6 indicates 6 inch of forward travel per revolution. ( less slip ) The weight of your boat will determine what pitch will perform best on your boat. In general a heavier boat will do better with a lower pitch angle ( 10-4 ) A lighter boat may do better with a higher pitch ( 10-8 ) Try different pitch angles on your boat to get the best performance. I suspect the factory prop is too low a pitch to do well on a Kayak. Party on Dude....

Can you do a Rigging of your Autopilot? Looking at the Helx 7 for finder. Not sure what mounts to get. Also, mounts for your Cannon Downrigger. I will be rigging a Auto Pilot 136.

Wonder if it would make a difference on a pdl drive?

Nice test. Was noise/vibration noticably different?

The standart prop is stronger for the water ,being more reliable.

Good test. 0.3mph increase is not a good trade-off for the prop jamming up when the motor stows. And........both props apparently present the same inertia to the motor as they draw the same current.

i Am thinking that the rpm of the two props have to be different. this may be the reason for the added speed. the motor will have less drag on the airplane prop than the bigger, heavier prop.

Not changing 😑 But have considered adding a second 100amp battery to the Yak.

What app did you use to find the current draw? I wonder if the same efficiency improvement can be had on the autopilot for bow (boat) mounted minnkotas..

Hi Tyler, Great post. I have a 46L # trolling motor that is too fast for kokanee trolling even at speed #1. I was thinking of purchasing the RC prop that you suggested an trimming it down to a smaller diameter. I know that this would be a trial and error thing but would this reduce my low end speed?

Hi Tyler, on different subject, what is the lure color would you recommend when we fish deeper between 60' to 80' of water for kokanee ? Thank you very much.

At 4 bucks a pop you could have many spares in case you break one (or two).

I want to conserve energy and get range. It seems like this prop on speed 4 might be my best bet.

Hi mate Wow ,,, if you had the trolling motor on the side of your kayak you could have a ,,,,,3 blade or 4 blade plane propeller,,, emagine what you might have achieved the mind boggles

I just purchased 2 of the props, I just finished putting a trolling Motor on my kayak. I Will come back and leave My results in the comments it will be in about 2

It takes a lot less torch to turn therefore the motor can rotate faster while not working as hard

Interesting

Ok I wonder if it would make a difference on the PDL series?

You need the APC. 10 x 5p works much better

Hey Tyler, have you installed this on your salty PDL as well? If nothing else I was thinking of getting a couple of these as spare props just to have on board

wonder how it will test in an Ocean setting with Current against the tide ?

Nice video Tyler. What app are you using to monitor the draw from your battery? Is it unique to that kayak and motor?

Hello Tyler, thank you for the video. It's been over a year and I was wondering if you still endorse the airplane prop for a trolling motor. Also how do they hold up. Appreciate the video.

Pitch of the minnkota tapers off towards the tip. Where the airplane prop Does Not. Of all the minnkota props I have seen, they ALL have this flattened tip...which Kills the thrust potential, effectiveness, and efficiency. A normal prop Does Not flatten out. The pitch is constant. The other factor is Drag. Minnkota has a Ton of drag compared to the airplane prop. Far as knowledge of pitch..it's Actually quite simple... A high pitch angle grabs more water/air i.e. Power, but will bottom out in for high speed. Low pitch i.e. Torque is going to give a higher speed, but takes longer to get there. (Example hydroplanes) This is based on the same exact motor.

Would you need to trim the airplane prop if you are not using it on a Kayak? I have an inflatable colorado pontoon boat.

FYI for anyone that is interested. This same company now offers a 10 x 5 prop that gave me and extra .5 mph on my Jackson big rig with a 30lb minnkota. I also have ordered the Jackson Kayak 10x 10 prop from them which I expect will give me a full 1mph increase with the 30lb TM (won't know till I get it). Their price is $16...about 1/3 the price on the Jackson web site. I don't know if this information will be deleted or not but thanks again for the heads up on these props. It really makes a difference when crossing a larger inland lake.

I noticed that your motor is mounted in centre and not at the back, what bracket or which min kota is that

just my 2 cents but there has to be a good reason why minnkota does not use the style prop you have demo'd here. I reason that thick weeds (seaweed) and sand would certainly damage the rc prop much more quickly so I am sticking with the original that has the beefy hub. Minnkota has decades of experience with these comparisons I would think...the extra 9-10 % speed boost is tempting but not worth risking the warranty concern or the more susceptible damage?? if it was titanium/aluminum alloy maybe, but then it would cost $100s for sure. Another great video, thanks for the effort. Keep it under 4 mph OK! Hah...

10x5M-LH

Can someone post a New link for the $4 prop? Please

Was his kayak loaded with fishing gear? “Horse” power to weight ratio comes to mind…

I'd like to know the difference in RPMs. Is the airplane prob spinning faster because it's lighter and the motor doesn't have to work as hard? Lighter with higher RPMs and a steeper pitch?

Hello, i dont have a question about the prop but about the deck matting you have in your kayak. Where did you purchase that from?

I am interested in the durability of the prop as it was designed for driving air not water - maybe a video of the flexing of the prop at speed.

You might have a different prop pitch than he did. You can buy different pitch airplane props for a given size.

Am I missing something? I don't see a link or any comment of the diameter and pitch you used.

What lake is that on?

Duc Tran has a 136 AP in his video and it maybe a faster kayak than your 120 AP, just a guess why he achieved a faster speed.