To those who want to convert a weed eater...

[friedlbug]

There has always been an issue with the bent shaft desgns being bent the wrong way. Things seemed to have changed a bit in the last couple years. Walmart is now selling a Weed Eater brand trimmer with a swiveling lower shaft (for lawn edging). The resulting shape angled correctly for use as a small boat motor. The trimmer also has a variable throttle trigger, manual choke, and 25cc engine. It's called the Weed Eater Max TE475. I did mine last night; there's not much to do. I swivelled the shaft, packed the end of the shaft with bearing grease, replaced the trimmer head with a Minn Kota prop (drilled out, the treaded end of the trimmer head attached this perfectly), and attached a short vertical pipe to the shaft with metal conduit clamps (the metal C-shaped ones for screwing conduit to a wall). Next I will put a recieving pipe on the transom of my duck boat. The pipe fom the motor shaft will pivot in this and allow for steering, the trigger will allow for throttle, the choke will shut it down (there's also a off switch), and the conduit clamps controll the angle of the shaft to the water and the depth of the prop. I've attached a very basic drawing for to the post. I'll try to test this as soon as possible.

[Black Swan]

Hilarious! Reminds me of the S.E. Asian "panga" type boats with a direct driveshaft and prop coming off the business end of an automotive engine and tranny.

[Kyle]

What a beautiful idea, Thanks. I have a canoe in mind that could use this set up.

[friedlbug]

Not so fast, guys. I tested this and found that the Minn Kota prop was pushing too much water for the motor's torque. The motor has a higher RPM than a normal outboard. I will have to modify the prop, but I'm concerned that the point at which the motor can run without stalling may not generate enough thrust to push the boat fast enough. Still working on it...

[Black Swan]

So... stick the prop in a lathe and "turn" it down to a smaller diameter, then test again. You'll eventually find the loading characteristic you're looking for.

[War Whoop]

Good Idea the shaft angle will be a lot more desirable.

[Jets]

A number of years ago a couple of my friends went on a canoe/fishing trip. The friends (identical twins) brought with them a "secret weapon" because they were too out of shape to paddle any distance. The second day they pulled out a "weed-eater" with an air prop from a hobby shop. and got the required power assistance to keep pace with the rest. The noise soon drove everyone crazy and it wasn't long before they they got capsized.

[Iikka Jokinen]

Not so fast, guys. I tested this and found that the Minn Kota prop was pushing too much water for the motor's torque. The motor has a higher RPM than a normal outboard. I will have to modify the prop, but I'm concerned that the point at which the motor can run without stalling may not generate enough thrust to push the boat fast enough. Still working on it...

I tried doing the exact same thing as you are talking about.. Not surprisingly I ran into the same problem. As soon as the prob hits the water, the motor cuts out. I am about to give up on this, that is unless you figured out a way to make it work? Please let me know.

Thanks,
Iikka.

[Jets]

1. Note that the boys used it as an air boat motor.

2. Perhaps this will at least explain the problem. Virtually all outboards have around a 1.5:1 gear reduction in the gearbox. That means that the motor spins one and a half times to one turn of the prop. A 2 horsepower trolling motor might even have a 2:1 ratio. Some racing outboards had a 1:1 ratio. Mercury had what they called a quicksilver lower unit (1:1) that practically required a tow to get started be cause the prop was too small to get the boat up on a plane. Now consider your 3/4 HP trimmer motor running at 6000 rpm... It might make a good blender with a 1 inch prop. To get anything meaningful out of the prop you need a reduction gear of probably 4:1. and then run a 2 to 3 inch prop. So far we are only talking prop diameter. you will need to consider pitch and the required blade area. I know that there was a company that sold a "marine" attachment tor these things but I can't find it.

3. http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=009931
This is Wooden boat Forum. I found it with Google search using "trimmer outboard" They are discussing plans purchased on e-bay

4. If you are still determined to do this, have a look at http://www3.telus.net/acboats/
They supply trimmer powered model remote control boats about 3 ft long. I believe they are direct drive but that they use a surface piercing drive and prop. All things can be done providing you can accept the drawbacks and limitations. In this case the idea does work well - in a model boat.

5. I have to admit that the idea is intriguing but Tanaka has already built a 4 pound 26 cc trimmer based outboard. Unfortunately they are discontinued. http://www.tanakapowerequipment.com/index.php?b=TOB300&d=4

[larry v]

I got courious and got the plans from e-bay. Found some minor flaws but the concept is good. (brass to stainless mating of gears, bearing doesent exiest) but it looks like it will work.

[firestorm]

heres a thought get a bigger trimmer I have a Sachs Dolmar 40cc clearing saw that runs a 12" blade and will cut down trees up to 5" in diameter. We used to use a 60c clearing saw by Huskavarna to cut christmas trees it had a 16" blade and you just pushed it under the tree and cut it down was fast and it worked well. also check into some of the attachments we have a little Ryobi 31cc weed trimmer that has a rototiller attachment if it will turn 4 10" dia tines thru the ground which it does fairly well it shoud be able to turn a prop thru the water. Just walked out and looked at it and other than rotating the gear housing to point the tiller shaft in the right direction looks like a simple mod and if it don't work you can allways till up your wives flower bed. there are also several small hand held tillers out there that could be modified to do the same thing. Also since the Ryobi has interchangible attachments you would still have a useable trimmer all you would ruin is the lower unit if it failed and the tiller attachment was about 80 bucks. As I have a 21ft boat I don't see me trying this so one of you guys will have to see if I am right or not.
Good Luck

[ddomp]

Take a look at my web site : www.weedwhackerboat.com. and tell me what you think. I have a United States Patent on the weedwhacker outboard motor.

[ddomp]

please visit my web site for your answers. www.weedwhackerboat.com. I also hold the patent on this product. Please feel free to contact me at sdomp99@yahoo.com.

[robrohdeszudy]

Hey there,
You remark on some minor flaws in the Ebay outboard plans. Any suggestions for how to address those flaws?
Thanks,
--Rob

[tomdeering]

Take a look at my web site : www.weedwhackerboat.com. and tell me what you think. I have a United States Patent on the weedwhacker outboard motor.

I don't mean to be unkind, but the video on your web site shows the unit works very well going downstream, but barely moves at all upstream. Either that or tthere is a stiff wind.

I'm looking at http://www.weedwhackerboat.com/videos/demo.mov and it appears at one point that the boat keeps moving downstream even midway through the turn, as if the current was what was moving the boat.

And, as the boat tries to move upstream, the camera zooms in. This hides the shore, which by comparison shows the boat is barely moving forward.

Tom

[flapdoodle]

I translated a Russian web page with a weedeater conversion here:
http://www.flapdoodledinghy.com/GD.html

The original site is here:
http://iv70.narod.ru/IV/9/GD.html

Bill

[tomdeering]

Just read the previous messages. Ignore all the people who say they THINK it will work, read the people who have said they TRIED IT. A string trimmer motor doesn't have the power to push a boat.

Yes, you can put the prop into a lathe and whittle it down until it's tiny enough so the motor doesn't die, but then you have a little toy that won't push squat. Yes, you can modify something with a much larger motor, but then it's not a cheap, light, simple thing anymore, is it? If you are willing to re-engineer a $500 brush saw, why not just go down to Sportsman's Warehouse and buy a $500 outboard which works correctly out of the box?

Think about it. If a 50cc trimmer motor would push a boat, why wouldn't Minkota make one and sell it? The reason is, because they would all be returned as non-working. Simple as that. Take a piece of string and twirl it in the air. Doesn't take much power, does it? Now paddle a canoe. Takes a LOT MORE POWER, doesn't it?

(I have worked on several related projects, both trimmer motor powered and outboard projects. There is NO WAY a small gas trimmer has enough power to push anything that will carry a man. You'll just have a noisy embarrasment that dumps oil in the water. Pour the oil in the water by hand and save yourself the noise and hassle.)

Still not convinced? Think the big outboard makers are hiding some genious secret from you? Then view the video posted by some pinhead who "patented" this "invention". It's earlier in this thread. See for yourself. It only works going downstream! That's right, it only moves forward if the water is already moving in that direction. When when he tries to move against a light current he zooms in the video so you can't see the boat isn't moving. (Ask yourself, why didn't he test it in calm, non-moving water? HMMM? Because it doesn't work, that's why.) If you're dumb enough to need a motor to go downstream, then this is the perfect project for you.

Sheesh.

[ripped off]

The only part of tomdeering's post that you need to pay any attention to is this:

"Ignore all the people who say they THINK it will work, read the people who have said they TRIED IT."

You just gotta love an internet expert :rolleyes:

tomdeering has obviously not tried it or simply gave up. I on the other hand HAVE tried it. I have built several of them and they work great. I started messing with them in the late 90's. ddomp's patented design is a carbon copy of the first prototype that I shared pics of on various web forums two years prior to his patent date, which is why I chose the name ripped off. That design with that prop is junk, believe me. But with the right prop in the right configuration it really comes alive.

I developed mine to power my layout boat. Despite what he says, you don't have to spend a fortune on a 50cc to make it work. I use a regular 30cc trimmer motor and can build the whole thing for about $150. Thats a scratch built drive, not just a conversion. They are also not loud as many people seem to think. You have to realize these are running about 1/3 throttle and under load, so you can actually talk to your buddy while motoring to the hunting spot. It's not like whirling a spool of line at 30000 RPM at some weeds. They will push a layout boat at about 6 MPH fully loaded. Mine has been in use for several years now, and I have pushed loads of up to 15 dozen decoys, myself and all my gear. I have towed another layout boat against a 20 MPH head wind, and can even break 1.5" ice. They will also get about 3 miles out of that tiny tank of gas.

You can see pics of my design and even instructions on how to build it on the weed wacker thread in the DIY Marinizing forum.

[ripped off]

Thought it didn't work.

Look, calm, non-moving water! And no $500 50cc brush saw either.

Theres probably about $60 in the converted unit and maybe $150 in the scratch built unit, including the cost of the powerheads.

Not the fastest motors out there, but just as fast as any other 1HP engine, and just right for the type of boats I use them on.

Pushing a load of 15 dozen decoys in a 14' wooden boat
http://i82.photobucket.com/albums/j244/Turn4fun/BigLoadatrivers.jpg

A couple of my motors. A cheap and easy "conversion" in the foreground and a scratch built drive in the back.
http://i82.photobucket.com/albums/j244/Turn4fun/Motorsatpintailchute.jpg

A buddy in an Otter Stealth.
http://i82.photobucket.com/albums/j244/Turn4fun/Swampy.jpg
http://i82.photobucket.com/albums/j244/Turn4fun/Swampysmotor.jpg

Video clip.
http://i82.photobucket.com/albums/j244/Turn4fun/th_Mudwackermovie.jpg (http://s82.photobucket.com/albums/j244/Turn4fun/?action=view&current=Mudwackermovie.flv)

[flapdoodle]

After the responses that it was not possible, I just had to do it.
http://www.flapdoodledinghy.com/motor.html

I could not be happier with my little 9 pound outboard.

Bill

[rangersboat]

This website is not working www.weedwhackerboat.com

Also, would'nt you be able to use a blower attachment as a propulsion system? just put it on and stick it in the water.

[Petros]

I have bought running garage sale weedeaters for as little as $20, I have bought running ones but with damaged heads for only $5 (I bought it for parts).

Looks like a fun little toy, maybe I can use it in my kayak, it only has about 4 pounds of drag at 4 knots if I recall.

[Fanie]

You have to use a smaller and smaller pitch prop. Also, don't start the thing out the water and push the prop in the water. Start it in the water so it's under load. You may also have to adjust the timing on the weed eater motor - it is set to run almost without load, you want to run it at full load.

[Robbmoffett]

Thanks for all the great info, I am reading Percy Blandfords old book (1962)[I]canoes and canoeing and he has a photo in the end of the book of a little kayak using a 1/3 HP motor. He says they are called sideboard motors and will push a canoe faster than can be paddled all day while doing 18 hours to a gallon of petrol. I am assuming he means English Imperial gallons, but still!! I am amazed at how much the little sideboard motors look like weedwhackers. I don't need to go fast, just want to see how far I can go on a gallon. I will be making my own weedwhacker motor and will let you guys know how it goes.

Robb Moffett

http://robbmoffett.googlepages.com/

[hallsj]

The only thing I can tell you is yes they will work. The following link is a short video of mine. I'm going to try a new gear reduction and prop combination soon... hope it works better; good luck
http://www.youtube.com/watch?v=xM6bBX4XZcc

[Jimbo1490]

Guys,

Do not overlook your local hobby store as a resource for props. Weedwacker engines are frequently used to power larger R/C speedboats. The propeller companies like Octura make props that are perfectly suited to your need with two, three and four blades, designed to dissipate 1 1/2 to 4 Hp and mid thousands RPM range. You will even get a selection of materials; plastic, beryllium copper alloy, or SS. Some of you may not have a hobby shop close by. Then there's always ebay. Look at item 260271240650. Yes the metal ones are pricey; that's the rationale behind plastic. What you do is take your first guess for the right prop and buy the pitch and diameter in plastic. you try the prop out on the water and if you think it's just right, buy it in metal. If not, try another cheap plastic prop until you find the 'goldilocks' prop for your boat/motor. A typical price for a good metal prop in your size range (about 3" diameter) is about $40. Plastic runs about $12. The manufacturers make a bewildering variety of these props, so it would be wise to seek advice from a knowledgeable seller.

Jimbo

[RangaTang@sea]

I cant find anything on that website about the weed whacker boatmotor. talk about hard to navigate. I am 13 and just finished my first outboard:~)! yay!!!
i made a prop that works like a jet ski does. it provides an enormous amount of thrust and it is all made out of scrap. it doesnt get to hot and only needs to run at half throttle to provide the same amount of thrust as a normal prop does at full throttle. it will always win against a conventional style prop and if anyone is interested i can post pictures of it.

[my432]

http://img86.imageshack.us/img86/3547/outboardstand.jpg
This guy figured out how to do it take a look. Free downloads... Check out the patent section.
http://underwaterprojects.741.com/outboard.html

[thudpucker]

I like my idea better: Using a Weedeater motor and a small alternator to re-charge the battery, that drives the Trolling motor, that drives the boat!

That way you only have to put up with that Obnoxious Weedeater while the Batter is being re-charged.

[srimes]

http://img86.imageshack.us/img86/3547/outboardstand.jpg
This guy figured out how to do it take a look. Free downloads... Check out the patent section.
http://underwaterprojects.741.com/outboard.html

Looks fake

[thudpucker]

[QUOTE=my432;296327]
This guy figured out how to do it take a look. Free downloads... Check out the patent section.

I tried to answer your PM but the Email format led my PC into a loop.
I have a photo of another guy's Weedeater battery charger.
I'm still looking for a smaller alternator, like a Motor Cycle alternator etc for my invention.

PM me with a good Email address and we can talk about it.

[MattZ]

Looks fake

I agree. He's claiming 8.8HP at the prop!

[Mark Wo]

It has already been proven that the 8.8hp is bogus. If you are looking to make a weedeater mud motor, jump over to this link. I understand there is much to read but every question has probably been answered here. I've now built 3 of these motors and couldn't be happier. The 2nd motor pushed my boat and my butt 6.2 mph and has been a dream to hunt out of.

http://www.boatdesign.net/forums/diy-marinizing/weed-eater-engine-conversion-1681.html

Mark

[armourit]

Here is a link to two old diy electric trolling motors that could be done with the weed wacker motor as well. one has a transom mount design as well
http://vintageboatplans.com/trolling/

Chuck