Hello,

I have a spare 750cc Ducati motor that I would like to purpose for a home built surface drive mud motor. It produces 70hp and spins at 9000rpm tops. Although, it stops building power at about 8k. I have no doubt that I will manage the build just fine. The question that I do not have the answer to is: What prop should I use? Is a prop made for this hp figure? Also, what rpm should I gear the prop to spin at for optimum performance?


Thanks!

Depends what kind of torque you'll be making for gearing

So it will have a transmission?

I will tell you from experience that you need lots of torque when testing a new motor. I had a 650 rotax and cvt tranny( out of can am outlander) and tried every trick in the clutching book including a $900 primary clutch and still couldn't get the low end torque to the prop. That same engine would pull the front end of the ground in the four wheeler on 31 outlaws but couldn't make the torque for a mud motor application, believe me I know

Yes. It has a 5spd transmission that is integral to the motor, as it is a motorcycle engine. I imagine I will simply put it in an appropriate gear and leave it there. The motor makes 45ftlb of torque.

i beleive the prop is designed to not spin over 2k rpms, your gonna have to gear it way down and hope you get it right. But you are wasting your time, all i can say

The first solid thing you hit you can kiss that gear good-by. But on the brite side you have 4 more to get you back to the drawing board!

I see you throwing a lot of money at this thing trying to get prop and gearing right. Tourqe is whats gonna get that prop spinning and you dont have a ton. If you run a huge prop your gonna have to gear way down which will make you lose the top end.

What kind of clutching system would you use? it seems like you would smoke a regular clutch.

-Greg C.

sounds like you need a centrifugal clutch

just sounds plain crazy, lol

Just me thinking out loud, but the CVT would work if it was setup to operate manually/lever. Pick what ever ratio you want depending on hole shot, top end, or rooten. It would also take the strain off the block and allow/maintain the higher rpms and run a variety of pitched props.