Some suggestions needed, 1 person mini speed boat design

[residentgearhed]

i come from the car world, so i know very little about the specifics and differences in boat designs. any help and suggestions would be helpful.

heres what i'm thinking:
design MUSTs:
width and height must fit in the back of a SUV/pickup (but length can stick out the back of the truck)
cheap and simple design
can be built by myself in my garage over the winter (i'm a decent fabricator)

design wants:
vee hull deign
single person boat
inboard motorcycle engine
dang fast

as far as the size goes, i'm thinking about 36" wide and a total height of 24-36". length should be about 10feet, not too much longer because i dont want it to stick out too far from the back of the truck and possibly snap in half from a large road bump.

things that i need to hammer out:
prop size. i dont have $1000 to get some crazy prop. can i use one from a small outboard engine or some other mass produced piece?

prop placement. under the stern of the hull? behind the boat all together? fully submerged? half submerged?

hull material. i'm good with fiberglass and plywood. either of those or any combination of the two would be possible, and more suggestions wanted.

fuel feed. if motorcycle engines (such as a suzuki 750cc street bike engine) is fed fuel by a gravity feed (tank is above engine) then how will i get the fuel from the tank in the bow to the engine?

i'm basically looking for something that i can stick in the back of a truck (NO trailer) and take down to a local lake or the ocean and tool around on for a while and then head home. basically no useful purpose whatsoever.

from some really rough calculations, a vee hull boat thats 36 wide, 24 tall and 100" long with a fairly shallow vee should support about 1500lbs before it sinks. i figure on the weight of the loaded boat with gas and driver to be about 700lbs. that would give it ~11" of hull in the water.

i'd be greatful for any help.

i've attached a REALLY rough sketch of the layout of the boat as i'm thinking of it. any input would be great.

[SailDesign]

I know this is not what you want to hear, but "Buy a JetSki" is the first phrase that sprang into my mind. If you can launch a 700lb boat from a pickup without a trailer, then a JetSki would be no problem. And vice versa.
If the idea is to have a home-built boat, then ignore the above
Steve

[residentgearhed]

yeah a jetski is pretty close to what i'm looking for, but imagine a jet ski that you sit down inside of.
the fact that i would build it is a large part of why i dont just go out and buy a jet ski. i imagine that a jet ski motor would be much harder to find and more expensive than a motorcycle engine (i was going to buy a wrecked bike with a good motor/electrical system).

i always enjoy building something myself and having myself and others see it and enjoy it.

[cyclops]

Water cooling a bike engine, never built- water cooled exhaust headers and pipes? Good first fabracation job. Aircooled heads are a beast in a slow moving boat in a swimsuit. Transmission is doable for tests. You can get a 350 CC ski for $350 to $500, used. Bikes on dirt -- jets on water. Don't mix well.

[residentgearhed]

i'm not sure what the majority of your post ment, but i gather that 350cc jetski's can be had for $350 to $500. any rough estimates on a top speed with a 350cc ski powered boat of the size pictured above?

are you saying that air cooled heads would make the driver hot in a slow moving boat? i get what you're saying and i would prefer a water cooled bike engine, but they are few and far between in my price range. plus, i'm hoping that the boat wont be slow moving

also not sure about what you mean with the transmission statement. i was thinking maybe dropping the tranny altogether and doing a direct drive, and possibly leaving just the clutch to allow for disengagment of the prop, although no reverse gear.

[cyclops]

You can not cover the air cooled engine. One good splash or flip over and your cylinders are toast and scrap metal. you can not do that to them. You need to ride some PWC or small jets to see what they can do. Do yourself a BIG favor. Bum some rides or rent a jet. Have a dealer take you out. Try it before you spend any money. Sound right?

[SailDesign]

cyclops - liquid-cooled bike engines have been around for a long time. Raw-water cooled? Nope, but they build heat exchangers for that kind of thing.
Steve

[residentgearhed]

does anyone happen to know of some bikes that came with water cooled engines?

and bump for more opinions on the above design.

[SailDesign]

The Yamaha ZYF-R1 (although most folks recognise it by it's nickname, R1)
Nice bike, way nice motor, prolly maore HP than you would want at this stage

[cyclops]

Are you going to cool the exhaust headers or bore holes in the hull and bail out the hull water? Noise should get you a ticket at most used areas. Only races get away with dry exhausts now.

[stephanabradley]

If you lay it out right - and by that I mean provide air movement with a fan or some similar device - you could have a dry exhaust with a muffler.

I am working on a similar design, but with a smaller motor and lighter boat built with cedar strip construction.

Stephan

[rickthorn]

I have seen something like you describe on t.v. recently. I think they are called "Sprint Boats", and they race around in small channels which are about 3 foot deep in what appears to be laid out in a sort of maze fashion.

[minispeedboats]

Hey All - Looks like I am 6 years late to this party! Great design idea - and some helpful tips on design. We would be interested in hearing about your project if it was successful.
You might be interested - we have just converted a Harley Davidson Crate motor to one of our F-15 model mini speed boats. Sounds just like the bikes and does a good clip too. I don't want to put any blatant advertising on here but anyone who is interested in checking out the specs feel free to send me an email and I will send some links. You should be hearing more about it in the coming months as we take it to market.

[upchurchmr]

residentgearhead
I have a friend who has tried to give me a 2 person, 10-12', 50 horse jet boat.
Already built, but you could probably have it cheap. You'd just need to come get it in Austin Tx.
If you are interested I'll contact him and see if it is still there.

Marc

[messabout]

An R-1, GSXR, or similar Japanese 750 is good for 100 shaft Hp or more. And you want to put that into a 36 by 100 inch boat??? Yes, I know that Jetskis are narrow and powerful but they are different breeds of cat. Sit on vs sit in changes the game considerably.

I fear for your life if you build a boat to this specification. Flipping the boat or getting into a blow over at 70, 80 mph is very unhealthy sport.

Build the boat as wide as the pick up will allow. Most pickups will allow about 42inches. You could use a cradle in the truck to raise the boat up over the wheelwells and get even more width. Consider a speedy little runabout design that uses an outboard. A two stroke 9.9 with an aftermarket lower unit will get you into a speed realm that is plenty thrilling and be a lot safer and far more practical than than the instrument of potential destruction that you have proposed.

Please accept my apologies for being a naysayer. You ask questions, you get answers, some of which you do not want to hear.