My hunch is that water-cooled motorcycle engines are essentially the
motive basis for many/most impeller-driven jet-skis.

The problem, methinks, would be in developing/creating a "conventional"
marine transmission (i.e. for a propeller-based boat) if only because
these otherwise powerful and light engines tend to produce best at very
high RPMs -- the reduction gearing needed would be, ummm, interesting...

I'm also assuming that you've already properly discarded the idea of
using an air-cooled V-twin... ;-)

- paul


ewan wrote:
this is more of a theoretical question more than anything else but a
couple of mates and i were chatting about boat building and engines in
general.

basicly ive heard a lot of engines are based upon marinised car
engine based but i got to thinking how simple it would be to use a shaft
drive bike engine {1} since theres a wide range of shaft drive engines
from 550s to 1100cc especialy the 900cc yamaha diversion engine which is
dirt cheap. i know the engines wouldnt last as long but sing they start at
£80 from breakers{2} means it could be treated as disposable item like
petrol.

im just posting to see if there is any serious flaws in the idea such as
not enough torque or other variables



{1} i guess i would have to work out the forces and calculate propeller
assuming the revs arent to high

{2} breakers tend to sell all the stuff that breaks in a crash like
plastic and bits that rust leaving them with the engine which most folk
dont want to replace