Mini boat power options

[stephanabradley]

Hello gang - my first post to this forum.

I am building a scale model of the attached boat, it will be done in cedar strip, very light. It is intended for my 9 and 10 year old boys, to use as a "toy" on a small lake here in Montana.

I am very familiar with small Tecumseh motors and Honda motors used in go-carts and the like. I was thinking of using one of these with a fan to assist in cooling and dry exhaust.

My problem is getting that power back to a prop and what prop to use? I could direct couple it, but my wife doesn't like the idea of hitting start and taking off!! Old race boats used to be built this way all the time, in fact, I have several drawings that show this very configuration.

Is there a VERY light transmission or some method to engage / disengage a direct coupled drive?

Any comments on the project as a whole are appreciated!!

Thanks,
Stephan Bradley
Bradley Boatworks

[gonzo]

centrifugal clutch

[duluthboats]

"go-carts and the like" Most of the simple ones use a centrifugal clutch as gonzo has suggested. A shaft break might be handy. Make sure the motor you pick can be run at an angle. I'm not sure how far you could scale down that hull without problems.

[stephanabradley]

I agree with you on the sizing, I just ran some calculations and this hull is just not the right one. It is a small boat anyway, so I will save it for another project.

I will just have to find the right hull or do some design work on this.

I think the centrifugal clutch is a good idea. I have a couple of hot-rod off road go carts that my boys drive alot here on the property. Both are using Tecumseh motors, 6 Hp, with what they call a torque converter. It works fine for that application with no reverse.

I also agree on the brake. As to alignment, I think it would be fine as long as I adjust the carb to a relatively level position - does that sound OK? The motors on the off-road carts are tossed around in just about the same way a small boat would move, so I don't see much of a difference. I might just go with the same exact set-up. They can be purchased for about $250.

My other thought was to use a jet pump, but I can't find one that small. I could make one I suppose, but that sounds tough. It would afford a bit of reverse, which would be nice.

[yokebutt]

Stephan,

Maybe not a good idea, but how about the power-plant from an old jet-ski?

Yoke.

[stephanabradley]

I have been looking at some of them, but the cheap ones are trashed and the good ones are really expensive. I was even thinking of building a axial flow pump and using a little Honda or Tecumseh motor. That sounds like it could be done, but sure sounds like a lot of work. I am leaning toward a 10 Hp electric start motor and the torque converter style linkage to the shaft.

I found a company that makes small jet pumps, but they will not sell me one, they just use them in their boats.

Check it out:

http://www.mokai.com/products.html

I think I could build something similar using an onld jet ski impeller.

Anyone else out there done something like that?

[maxwell]

Im in the same boat, looking for propulsion options for a 14' glass boat. I also decided to go with a jet, and am still in the reserch and development stage. check out solas.com it might be worth the 200 clams for an impeller if you could figure out what size, pitch, and all of that stuff. also for a 9 and 10 year old no exposed prop is definatly a plus. any progress let me know

[stephanabradley]

Thanks for the link and I will look into it further, but it looks like I am going with a direct coupled 10 Hp electric start Tecumseh motor. I just need to find a prop. My project is very light and I am trying to sell at $3,450 or less. The typical jet pump would cost more than the boat.

Stephan