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.

Originally Posted by 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...

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/ultim...c;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/...p?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]

Originally Posted by 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.

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