[tanshi]

Im bouncing around ideas for the future and so thought i would get peoples opinions, not doubt there will be some haters but im prepared for that.

Im looking around for bigger capacity two stroke engine options for a TT style build. It occured to me that an EFI jetski motor might be nice and powerful enough.

My Question is does any one else have a better idea. ??

Will a Jetski motor work with a constant changing revs. Cooling issues?

[Zook_Fan]

In what? A jetski?

[Chop]

Rotax 1000cc

[tanshi]

posted before it was finished.

Looking at a possible LJ50 TT build

[atari4x4]

Chop wrote:

Rotax 1000cc

this!!

seen a 500cc rotax work really well in a formula 500 speedway car.

[tanshi]

obviously gearing would be an issue to make sure of keeping the revs up in the right range

[Fatzook]

1000cc supercharged Rotax from a Seadoo jet boat.

[N1K]

GP1300r Motor. Fuel Injected and 3cylinder ?
Also have a power valve option when at low revs the exhaust valves close keeping the compression up

[Fatzook]

Fatzook wrote:

1000cc supercharged Rotax from a Seadoo jet boat.

Scratch that. They are all 4 strokes

[tanshi]

hmm, can pick up a GP1300r for about 5k

[Gwagensteve]

Apparently this has been done- with something like a 900cc jet ski motor. I haven't seen any info, I was just told about it.

Does anyone else remember the 2 stroke race flat 6 someone was putting in a rock buggy in the states? Motor weighed something like 50kg, and made 300hp @ 14000rpm. It was going to be stepped down into a 'glide 2:1.

Steve.

[tanshi]

does any one else think there ould be any issues with cooling?

i cant imagine adapting to a gearbox would be insanly hard

[N1K]

Yeah all the supercharged ones are 4stroke, the 1300 is the biggest 2stroke they made for skis.

If you want to keep it all suzuki there is a 3cylinder 2 stroke 900cc suzuki motor that was used in the Arctic Cat, Tigershark jetskis.

I had one and it flew!!!!

[tanshi]

all suzuki would be sweet. but 2 stroke would be the main thing.

might have to trawl the US. the engines are small enough that they would be cheepish to ship

[want33s]

Gwagensteve wrote:

Does anyone else remember the 2 stroke race flat 6 someone was putting in a rock buggy in the states? Motor weighed something like 50kg, and made 300hp @ 14000rpm. It was going to be stepped down into a 'glide 2:1.

Steve.

Yep. Was a MERCURY "TOWER OF POWER" 6 cylinder. Haven't heard anything about it for a long time though.

[tanshi]

are most of the newer ones fuel injected or carby?

[Gwagensteve]

Agree want33's- the thread just stalled. Very cool idea though.

Steve

[want33s]

V8 Evinrude 3.6l in a sand rail....

http://www.youtube.com/watch?v=lRKeuHyI ... e=youtu.be

http://www.youtube.com/watch?v=y11aYD99 ... e=youtu.be

[N1K]

Most new ones are fuel injected. But in saying that i think that Yamaha were the only ones that made 2 stroke sit down skis. You can still get 2 stroke standups but not sit down skis.

You mean newer 2 stroke skis?

Also i remember seeing a buggy a while ago on youtube running twin YZ 500 2 stroke motors.

[want33s]

Can't find the outboard buggy mentioned /\ /\ but heres a V6 2 stroke outboard in a buggy.

[tanshi]

thats great Jas, i suppose the other things to consider are things like hydraullic pumps, alternators, etc

[want33s]

Alternator shouldn't be too big a deal... Most outboards over about 25hp all have some sort of charging system. Wether it'll be enough to run a car I don't know.

Check the specs at Suzuki or Honda or Mercury etc websites.

Hydraulic pump can be run off the flywheel just like mercury's ran the distributor (A section V belt) .

OR...
Make up a drive plate and run hydro pump, water pump and alt all off the flywheel as in the top pic.

[Scrawny]

Most skis run water cooling thru the exhaust, not sure whether that's absolutely needed? You'll need to run some kind of heat exchanger system i guess. I like the idea tho

[JrZook]

How much HP are you looking at? OB powerheads will have a fairly broad torque curve which would be a good thing. Anything that doesn't have a carb will be getting pretty pricey tho.

Jetski motors may be more easily converted for use in a vehicle as the crank runs horizontal with intake and exhaust on opposing sides. Example of Kawaski 800cc twin:



Shouldn't be an issue running closed loop cooling on them. Just have to omit the water cooled exhaust and make up some descent expansion chambers

[tanshi]

power wise, something usable without being huge.

something with ~100kw i would think would be plenty,

similar to g16 powered territory i guess would be enough

[want33s]

Scrawn wrote:

Most skis run water cooling thru the exhaust, not sure whether that's absolutely needed? You'll need to run some kind of heat exchanger system i guess. I like the idea tho

95% of the reason for that is to (try to) make them quiet.

JrZook wrote:

Shouldn't be an issue running closed loop cooling on them. Just have to omit the water cooled exhaust and make up some descent expansion chambers

The big hurdle you'll run into is the jet ski motor is not pressurised. Most conventional cooling systems run up to about 13psi.... Can a jetski motor handle that?

[ball]

atari4x4 wrote:

this!!

seen a 500cc rotax work really well in a formula 500 speedway car.

494 rotax 100+hp rotary valve

My cylinder head thread that is here somewhere was for this particular breed of engine

[sideways]

The hardest thing about a jet ski engine would be mounting a flywheel/flex plate on it, they all seem to be spline driven. Absolutely tiny splined shaft for the HP output too.

I've got a Mercury 50hp outboard (4cyl 2 stroke) that I've been playing with. It's a lot more work than a jet ski motor but hey, it was very cheap and I like to tinker. Basically that needs an engine cradle to mount it, some barrel work to get around the exhaust that comes out where the flywheel should be (Mercury accounted for this, there's a plate you remove so you can fit expansion chambers for racing applications), the ignition timing is controlled by throttle position alone, you have to fit a flywheel to it and bolt a plate to the bottom of it so you can fit it to a gearbox. You then have to figure out how to mount an alternator, P/S pump and water pump, the engine cradle makes that all pretty easy though. It'd actually be 100x easier to fit a flywheel to the front of the engine, but that makes everything else harder.

Where as Jet Skis tend to have car style engine mounts, have a much more sensible exhausts, more performance based engines (so probably better built and can take more revs, plus more parts around) and there should be a lot of good info on them around.

Looking just at the Merc, here we have an engine that weights almost nothing, is very compact, makes max (well, quoted) power between 4800 and 5300 RPM so has a wide power band at relatively low RPM and being an outboard, it should be somewhat reliable (insert laughter from boat owners here).

[royce]

Dont Jetski engines cost 4 million dollars to rebuild every 3 days of use?

Also, cooling systems are only pressurised to increase the boiling point, no need for it to be

[tanshi]

yeah possibly, thus im also looking for all other options.

15kw out of a stock lj50 motor really isnt going to do it