Lawn Mower Engine Jet Drive

It sounds like a home made Water Jet drive

http://www.hamjet.co.nz/

are the 'original' innovators, and there is some history on the link - somewhere .

But you will find dozens of jets around now, in boats spanning recreational through to ferries and military.

34point5,

Thanks for the link. The reason for this recollection was the recent introduction of Briggs & Stratton outboard motors.

The river I mentioned has some very shallow backwater areas and I suspect this type of drive would be practical. Some guys here have outboards with jet drive lower units, these are very expensive.

I wish it was summer!

Jets are fairly inefficient at low craft speeds - say below 30 knots.

I.e. a 'naked' propeller is the better device for most boats.

I take it by "jet drive lower units" you meant?

What you might consider is what I know as a Kort nozzle, or shrouded prop.

They're used on tugs through to nuclear subs for - well - their 'tug' from zero boat speed and quietness in the higher ranges. Obviously there is a larger drag loss at high speeds than a supercavitating prop, but no 'acceleration lag'.

I think a shroud would be particularly suitable for a tunneled hull - and a 'short leg' outboard combo.

Not quite how I'd do it - but if you 'add the pictures' I'm sure you'll get the drift.

And a fair part of the choice depends if your hazards are rocks and/or weed - as opposed to fine gravel and sand.

There are actual impeller type jet units that bolt on in place of the lower unit for most mid sized outboards now. They are used extensively here in the north. Quite a few folks have built custom jet sleds or jon boat type units similar to what was described with all sorts of power units attached. Most however rob the propulsion unit from a jetski and graft it into the hull of choice and proceed to have a ball. Variety is the spice of life.

This is an interesting drive for when the going gets tough (muddy).

See here.

Cheers,

Stu.

Hehe, just so happens I saved this earlier

Super cavitating surface piercing dual propellers. Design to run partially submerged and operate in the cavitation mode. The cut off blade ends release pressure

Well! Now that you mention it.

Here's mine with a 500hp lawnmower engine.

Launch day.

Stu.

That prop is 800mm diameter. Scoots the boat along at 30 kts. max.

Next is Mk2. Just wanted to know what would happen if..............?

We spent a bundle doing that.

Sorry! upside down.

Ahh! Howard Arneson!

Genius! Flamboyant showman.

Mate of mine actually got a ride in the "beast" on San Francisco harbour. Howard then showed off by afterburning the exhaust on the engine. Huge plume of flame. All at 160 mph.

The big cat was powered by a gas turbine, which allowed this showing off.

Only Howard....

He developed the steerable/trimable surface drives. The other Italian drives (Levi) were fixed like mine, but not nearly as controllable as Howard's, but WAAAAYYYY cheaper, even tho' the prop cost ten grand. The Kiwis took a shot at 'almost' copying the Levi, called the SeaFury. Worked OK on some specific boats, although they would have you believe that they were a panacea. NNOOOOOOOO!

Spent 50 years messing around with this stuff. Could go on and on and on..........But won't.

Cheers,

Stu.

I used to moor my boat in a marina off San Francisco Bay. The boat that had the Arneson drive(s) was a Chris Craft catamaran driven by twin gas turbines. It was owned by a doctor and called the boat the "Surgen Sturgeon". He would leave my marina, head out into open water and then open it up. He would arrive on the other side of the bay around a minute later, judging by the sound. The boat was used for offshore racing, but piloted by a professional driver. That was back in the 80's.

"Could go on and on and on..........But won't"

How about if I bribe you?

Take a look at Mokai.com to see a similar setup. This mentions a subaru engine, but I seem to recall that they were using a Honda unit earlier. Quick removal of the engine for transport and storage, as well as the water jet you wanted.