Inboard DIY race motor

[microbream]

Hi Guys,
I enjoyed Ron's DIY outboard race motor and it got me thinking?
How about using the same ohv 4 stroke motor and mounting it inboard?
connecting straight to the prop shaft via a auto cv joint should do the trick.should be both lighter and more efficient.
Or to go realy balistic how about a air cooled 250cc MX engine and gearbox!
now that would be interesting.
has anybody tried something like this?
cheers
Kael

[Skoontz]

Have plans for a 12' cracker box type boat that I wanted to power with a 600cc Suzuki Katona motor turned sideways. I put a lot of thought into a smaller inboard, and felt the weight ratio to power drained from the driveshaft would have to balance out around the 600cc/80 HP mark, and depending on propeller selection, you got a redline at 12,500. Just hook the driveshaft to the tranny and you got 6 ratios in which to play, and you can even use the factory instrument cluster.
Its been years since I played with any lawn mower engine type performance, but the amount of fiddling needed when we ran them on mini bikes was extensive, and hop up parts had to me made. With a motorcycle engine, you can buy a great deal of the stuff already made!
Now that I've been accepted as a volunteer at the Lake Tahoe Maritime museum at the restoration projects facility in Truckee, they will let me use the space to build the boat....But then there is the time...I've only budgeted a day a week to volunteer and all else taken with projects. Keep us posted about what engine you may want to use and your project.

[Fastjeff57]

There's a U Tube video out there of a guy who put an inboard prop setup on his jetski. Close enough. But I got to tell you about the paddleboat racers of western Kentucky.

If you're thinking "Delta Queen" of those little peddle cars, forgetabouit! We're talking full out BEASTS with really simple class rules: The boat must be propelled by a paddlewheel. Period!

A typical entry was my buddy's, powered by a Honda Gullwing MC engine connected to the paddlewheel. He starts off in LOW gear, then upshifts after the boat's on plane until he hits 5th or 6th at the turning pylon, then downshifts a few gears to get moving again. Far out, eh?

Well, that's nothing compared to the Rainmaker! S B Chevy powered (through a Powerglide, as I recall) to an astonishly fast spinning paddlewheel. Down the straights at 60 mph, throwing a rooster tail a hundred feet high! Whoopppee!

Jeff

[microbream]

There's a U Tube video out there of a guy who put an inboard prop setup on his jetski. Close enough. But I got to tell you about the paddleboat racers of western Kentucky.

If you're thinking "Delta Queen" of those little peddle cars, forgetabouit! We're talking full out BEASTS with really simple class rules: The boat must be propelled by a paddlewheel. Period!

A typical entry was my buddy's, powered by a Honda Gullwing MC engine connected to the paddlewheel. He starts off in LOW gear, then upshifts after the boat's on plane until he hits 5th or 6th at the turning pylon, then downshifts a few gears to get moving again. Far out, eh?

Well, that's nothing compared to the Rainmaker! S B Chevy powered (through a Powerglide, as I recall) to an astonishly fast spinning paddlewheel. Down the straights at 60 mph, throwing a rooster tail a hundred feet high! Whoopppee!

Jeff

Wow i have gotta see that!!!!!!

[Skoontz]

I dont think the torque will come in to play as much as if the size is there. More size is more torque. The thought behind motorcycle engines is that stuff is available with about any hop up bolt on you can find for dirt cheap. Lots of crotch rocketeers find their ways around trees and guard rails with very low milage on the motors, where a jet ski engine by the time you find something cheap enough is going to be plain worn out. But we can bench test this stuff all we want. My grandfather had a plaque on his test tank that bore this inscription. "One test is worth 1000 expert opinions"

[microbream]

I dont think the torque will come in to play as much as if the size is there. More size is more torque. The thought behind motorcycle engines is that stuff is available with about any hop up bolt on you can find for dirt cheap. Lots of crotch rocketeers find their ways around trees and guard rails with very low milage on the motors, where a jet ski engine by the time you find something cheap enough is going to be plain worn out. But we can bench test this stuff all we want. My grandfather had a plaque on his test tank that bore this inscription. "One test is worth 1000 expert opinions"

yes there is no substitute for cubes at the end of the day.
makes me think about using a 250cc mx engine 40+hp and six speeds !

[microbream]

Have plans for a 12' cracker box type boat that I wanted to power with a 600cc Suzuki Katona motor turned sideways. I put a lot of thought into a smaller inboard, and felt the weight ratio to power drained from the driveshaft would have to balance out around the 600cc/80 HP mark, and depending on propeller selection, you got a redline at 12,500. Just hook the driveshaft to the tranny and you got 6 ratios in which to play, and you can even use the factory instrument cluster.
Its been years since I played with any lawn mower engine type performance, but the amount of fiddling needed when we ran them on mini bikes was extensive, and hop up parts had to me made. With a motorcycle engine, you can buy a great deal of the stuff already made!
Now that I've been accepted as a volunteer at the Lake Tahoe Maritime museum at the restoration projects facility in Truckee, they will let me use the space to build the boat....But then there is the time...I've only budgeted a day a week to volunteer and all else taken with projects. Keep us posted about what engine you may want to use and your project.

That sounds great, have you thought about a jet ski engine? I think the biggest problem with motocycle engines is lack of torque, even if you used a gearbox i think the boat would would slow down too much between gear changes.
will you run a cleaver prop and what angle would your propshaft be?
i have done some more research for my project and a briggs and stratton world formula go cart race engine has 15hp and weights just 15kg.
will run up to 7000rpm . Obviously hop up parts are every where. Another option is a subaru kx21 race engine.
Both are 200cc single cylinder air cooled 4 stroke ohv. My hull will be a 10ft aluminum jon boat .
cheers kael