2 stroke Jet Ski engines

[flykr]

Has anyone looked into these engines for a microlight, power ranges from 80-130hp? Layout is the same as the Rotax 582... some are even made by Rotax??

[Morph]

there is a 583, that is what looks like a hotly tuned 582. What they don't have is the dual ignition systems and gearboxes. There was a thread about this a long time ago. I'll try to find it

[flykr]

The one's I've seen look like the 618 engines with the single ignition. The taper on the crank looks the same but this would oviously need to be measured, I'm sure you can make an adaptor plate to fit a B or C gearbox. A new 110hp engine costs R25k for a short block so the price looks good, I'm not sure if the cooling will be an issue

[Morph]

Not sure if you could use a standard gearbox because these motors rev higher than the normal 6800 in order to produce the power.

[flykr]

I never thought of that. I suppose it also depends on what aircraft you are fitting it to. I'm looking at the higher prop speeds (3500rpm max - 52" prop). .... so should be able to find a gearset to match engine and prop rpm.
The plane I'm building has a VNE of 200mph and I'm trying to get a cruise of about 190mph. I'm currently fitting a 503 but would like to change this later on once she is flying.

[Massimo]

Do yuo need to get somewhere in a hurry

[flykr]

Nope….I just like the speed - although flying low and slow is also nice.

The problem with the KR1 I'm building is she cannot carry the weight of a heavy engine (wingspan is only 5meters).
I would love to get my hands on a Jab 6 cylinder but just cannot afford it, there is a KR1 in the states with a 120 hp 6 cylinder Jab engine that cruises at 230MPH and climbs @ 2500fpm. ....

[Morph]

I never thought of that. I suppose it also depends on what aircraft you are fitting it to. I'm looking at the higher prop speeds (3500rpm max - 52" prop). .... so should be able to find a gearset to match engine and prop rpm.
The plane I'm building has a VNE of 200mph and I'm trying to get a cruise of about 190mph. I'm currently fitting a 503 but would like to change this later on once she is flying.

with that prop you are looking at

RPM 6500 (max cruising rpm)
gear ratio of 1.86
prop length 52"
prop rpm 3500
tip speed 793 ft/sec. (stay away from speed of sound 1082 ft/sec)
Effective pitch = 58 (true pitch 75 and prop slip of 23%)

this will give you an airspeed of 193mph. Don't think you will be able to get a 503 running at 6500 with that pitch.

Here's the spreadsheet with these calculations

[flykr]

I'm using a 2:1 ratio on the 503 and have been advised (by our local prop maker) that the 503 can turn a 52/53p prop using this ratio. With the 2:1 ration full power @ 6600rpm and 3300 prop rpm a 53'" pitch should give me 160mph. I'm not so sure the 503 can turn a 52/53p, what you think Morph?

I recon the 503 can only turn a 52/36p using a 2:1 ratio….but then I'm not an expert on prop's.

[Morph]

I don't think it has enough power. As you up the pitch it loads the motor, reducing the max rpm.

My Challenger had a 60" prop with a 44deg pitch and it only managed to get 6250 max rpm. (but that was on a 2.6:1 ratio)

[flykr]

Hmmm, and you're at the cost… here are some stats I've gathered over the years using VW direct drive engines @ 5400ft:

- 2L type 4 (Estimated 65hp - 95ft/lb torque) turns a 52/41p 2900rpm max
- 2L type 4 turbo (Estimated 90hp+ - 125ft/lb+ torque) turns a 52/49p 3300rpm @ 32" boost
- 1834 VW type 1 (Estimated 60hp - 90ft/lb torque) turns a 54/32p 3200rpm max
- 1600 VW type 1 (Estimated 50hp - 75ft/lb torque) turns a 52/32p 2850rpm max

I'll see how things pan out when I do static tests using a 52/36 test prop.

[Morph]

This is where you need a ground adjustable prop, preferaby a 2 blade (more efficient than a 3 blade by a few percent). You can experiment to your hearts content to get the best pitch/static rpm

[Miskiet]

Your speed range is huge - Ideally you need an in flight adjustable prop. You might be OK at 190 mph but you sure are going to need a long runway to get off the ground.....