Check here to get the history.
http://godevilalaska.wordpress.com/

It just wasn't fast enough on my big boat.
I couldn't get the prop to surface with the CVT so I parked it while I thought about it for a year. I've removed the CVT and installed stock GoDevil sprockets and belt with a 1.5 to 1 ratio. with the engine tach at 900 rpm my prop tach reads 600 rpm. This will give me a little more torque at the prop than the 1.4 to 1 ratio they use on the 35 SD. The toughest part is getting the motor output shaft and the prop input shaft parallel and aligned. I think I've got that licked and now I have to be patient until spring. I hope breakup comes early this year. The little Kubota purrs like a kitten. I ran it up to 3400 rpm last night. It's surprisingly smooth and quiet. The books say it will burn under one gallon per hour at 3400.
__________________
So many rivers, so little time.

SO; STU, If you gear the prop down and reduce its RPM how will that increase your speed ? With the deisel you should have suffecient torque and should be able to gear it the other way. So when the engine turns 600 RPM the prop turns 900 RPM. That would increase your speed. UNLESS you choose to change the prop out which changes to whole equation.



The CVT didn't get sufficient torque to the prop so it wouldn't go into surface drive mode. The diesel is a Kubota D905E 3 cylinder. This little jewel puts out 26 gross hp at 3800 rpm and about 39 ft-lbs of torque at 2400 rpm. This is actually close to the 27 Kohler specifications. I'm hoping that going to the 1.5 to 1 ratio I can get 16 -18 mph with my 24 X 48 Alweld. I'm trying to get it to swing the 35 hp GDSD 3 blade prop. For those of you that have the need for speed... I don't. I want fuel economy for my 300 to 500 mile trips on the Yukon. The Kubota burns under 1 gallon per hour at WOT. If I can get this to work I can double the fuel economy over my 35 GDSD.

WOW! That thing has got to be heavy. Cool machine though.

thanks for sharing this info

That's what I was thinking the only way that this would increase your speed would be that it let you swing a bigger wheel. I agree fuel burn is extremely important where you travel !!
Some CVT have an overdrive factor built in as well, that could damage your output torque. I'll have to drop by and take a ride up the Chena or something. Best of luck with your project.