Used hydra-drive

Searched the internet, searched the forums, couldn't find much info. Hydro-drives, made by Yamaha. They use some kind of hydraulic clutch with disks to change gears smoothly. This is something I would really like.

So a guy offered me one for just a few hundred bucks. He also said it "only needed new top gears", because they were worn out. I could also choose between a 22", 23" or 24" prop.

But I wonder... There isn't that much info I can find. The info I did find was that the oil needs to be changed regulary. If you didn't, gears could wear out fast. Also, the metal particles and shavings could mess up the hydraulic valves. Be it just getting particles, which causes them not to close, or maybe even just real damage to them.

But I have more questions... The internet told me the (early) drives were intended to be used on 300 hp V8 engines. I want to use a 2.4 liter engine, with "only" 165 hp. (and 230 Nm of torque) Engine would also hit about 5.500 rpm. Would even a good hydra-drive like that work for me? Can the shafts and gears handle that RPM? Can I just put on a tiny prop to compensate for the lack of power? (looking for a top speed around 70 km/h)

Any and all thoughts on this, and scraps of information, are very welcome!

 

This Yamaha drive was quite short lived in the US market and I suspect was reacted to similarly over there, so finding parts for these puppies is all but impossible. They didn't make many, nor sell many, though were considered reliable if well maintained, not so much if neglected. If you only need "upper gears", this was a neglected drive and a complete tear down is in order, if only to remove all the little bits of metal floating around in the fluid. This metal particulates don't just "mess up the hydraulic valves", but destroy the internals, shafts, seals and bearings.

Again, fitting this puppy to your V6 will present gearing issues, as the V8's it was intended to live with, operate at a different RPM range than your V6. This drive also takes a costly solid hub prop, instead of the typical rubber insert prop.

Each engine type that powers a drive, will have different horsepower and torque ratings, plus these specifications must be matched, to the correct outdrive gear ratio, to get the maximum power transfer from engine to propeller. Even if you don't want the "maximum" output, you still need to be close, so you don't break stuff. You V6 will not break this Yamaha drive, as it's designed for lots of torque and HP, but it will be way off its operational range, because of the gear ratio, that's designs for a GM mark IV big block. A different prop might help, but maybe you should price out what custom props cost, for this particular drive.

 

Thanks @PAR! You confirmed everything I feared, and then some more. The hydraulic gear shifts would be the only nice thing about this kind of drive. Everything else is just not for my project. I'll inform the person who offered me this drive that I am not interested.