High speed, low horsepower???

[Squeakit]

I would be very interested in knowing how to get the most speed from, say, a 3hp outboard on whatever kind of boat. I've seen lots of stuff on high-powered machines, but what a challenge to wring the most you can from a little kicker. I'm not talking about hopping the motor up and running nitro for one good run before it melts - I'm talking about something that will zing along at a good clip using a little kicker. Anyone with a fat wallet can buy mega-power. Anybody out there ever experimented around with low-power low budget stuff?? Just curious.

 

[NathanY]

Re: High speed, low horsepower???

Use to do it with Briggs and Stratton 5hp engines on carts. Would take and put different piston and valves, and carbs in them and make it into a full blown Alcohol machine, could easily make 15-20hp motors out of them. But that required alot of machining and alot of calls to wisco to get new pistons. Dont think you could do that with a 2 stroke. They already have a high rev limit, and dont think alcohol would mix very well with 2stroke oil.

 

[rterrian]

Re: High speed, low horsepower???

It can be done ,but it's a whole lot cheaper to but a bigger engine.

 

[rterrian]

Re: High speed, low horsepower???

It can be done ,but it's a whole lot cheaper to buy a bigger engine.

 

[Yepblaze]

Re: High speed, low horsepower???

Buy a 3 or 4 foot balsawood model and control it remotely.<br /><br />I'm not sure, but in order to get a 3hp motor to put a boat up on top of the water, with a person onboard, couldn't be big or heavy, even if it was possible.<br /><br />Maybe a canoe would be fastest. They don't have to plane.

 

[Squeakit]

Re: High speed, low horsepower???

I have an old 3.5hp air-cooled Chrysler that just about planes my 12ft aluminum boat with me in it and nothing else. My 3hp Evinrude is slower (has a weedless prop which is angled down and gives less thrust) I had a 4hp Sea King (Gale) that would plane the boat. We're not talking eye=watering speed, but not bad for a little motor. My 5.5hp Fisherman jumps the boat up on plane and moves it right along - wish the pressurized gas tank wasn't so heavy. Sometimes it's hard to tell when the boat is planing at these slower speeds when I'm in it. Oh well, I've got a little boat and a lake to play with it in and it's fun! Wonder if anyone has tried putting an outboard on a surfboard?

 

[FlyBoyMark]

Re: High speed, low horsepower???

Motorized surfboards were a thing of the 60's There is one company that makes a thing that actually pulls you around on skis...but then again whats a jet ski?????<br /><br />Go here for current stuff of today:<br /> web page

 

[Chinewalker]

Re: High speed, low horsepower???

The Antique Outboard Motor Club has a popular event called the Fishing Motor Derby with motors limited to 6hp. There are stock and modified classes with some of the mod guys going whole-hog on some of these motors. They use light plywood and aluminum boats and can move at a good clip.<br /><br />Of course, the ultimate in power to weight ratio is the world of Stock Outboards (www.apba.org). I get well over 60mph out of my 24-cubic inch (approx 30hp) Yamato on a small flat bottom C-Stock runabout. The hydro guys get over 70mph with the same engine. The A-Stock guys run the little Johnrude and Mercury 15hp motors and are getting over 50mph. The J-class kids used to run the 5 and 6hp Mercs and could approach 30mph. <br /><br />Bottom line on high speed with minimal power is improving the power to weight ratio. You need JUST enough power to plane off the boat, and all the rest is speed. Getting a boat planed off required much more power than getting it to a higher rate of speed once on plane. Some of the afore mentioned J-stock drivers have to be THROWN on plane by their pit crews...<br /><br />- Scott

 

[Squeakit]

Re: High speed, low horsepower???

Terrific and interesting replies, guys. I'm getting an education. Questions: what is the smallest aluminum boat available that will seat one 150lb adult? What is the absolute minimum hp required to plane this smallest boat with aforementioned adult in it? What is the lightest weight outboard 5hp or less - including older motors? I have a Yamaha 2hp that I increased the power noticeably by opening up the idle relief ports and replacing the plug with a type BUHX, but I don't think I can get a 2hp to plane anything unless I strap it on my butt and lay down on a boogie board. How do you THROW a boat on plane?

 

[FlyBoyMark]

Re: High speed, low horsepower???

8' jon boat by Landau..But here is something to consider....planing area to weight ratio...a small surface hull may not plane as good as a 10' hull on the same horsepower (less lifting surface). I had a Alunicraft 12'L X 36" wide jon that would do 30 mph with me in it. Same 15 HP motor on my sons 12 Sea Nymph 12r v-hull...25 MPH. If the wetted surface gets too big it will slow you down again because of drag also.