Classic Australian Wooden Power Boat Association

I hope this subject is not taboo !

But...can I use a jet ski engine , and attach a prop shaft as direct drive without the jet unit. I would consider using the jet unit but is seems you lose a lot of HP . I must admit that I am a little confused how this might work.......I am hoping someone will enlighten me.

Stuart

Stuart, what, is Old Flame too slow now? Most jetski motors are derived from bike engines except for the hard marinising work already done for you. The important piece of work would be to separate the jet unit but make sure you keep the thrust bearing.
Alan.

Most Jet Skis seem to have plenty of horsepower to spare and Jets have there own joys.

Alan , Old Flame is just fine...

Heres the question, i know of a 70 HP jetski engine with jet drive in a small hydro does 35 -40 mph , but with that sort of HP it should do at 60 mph + . Does the jet drive system gobble up that much HP ?

An outboard with 30 HP will do 60 MPH.

I assume jetski engine rev 6000 plus.

Yes i am looking at using a Jetski engine or alternatively a small very light (and cheap) car engine direct drive to prop shaft in a very small hydro style boat.

Any suggestions.

Stuart

Stuart they run prop modified jet ski engines in the one litre clsss hydros in america. They fly.

Stuart,
like Dave said the prop as usual is the key, the jet will always be less efficient due to the change of direction of the water, but should still perform well if the impeller is set correctly. As far as a small engine any bike (water cooled) unit should be fine, my favorite would be K100 BMW, water cooled, separate engine gearbox with a dry clutch, real Alt, good low torque and 100HP from an inline four that is basically a little car engine on it's side. They even ran them in an open wheeler like a like formula Ford in Germany a few years ago.
Alan.