Donzinator - Don't worry, I'd keep everyone informed! With the amount of room I've got in my engine bay I could happily just 'give it a shot' to see what happens!

Thirdchildhood - I see what you mean now! Funny you should suggest that, it was my initial idea, but with much longer springs and most likely using tension springs instead of compression. The springs would still have to be matched to the output torque, but a range of springs for various base hp wouldn't be the end of the world.

James

A boat application would be too dynamic for a fluid coupling, at least a commercially available one. You can find the spec sheets on the web and see how they transmit power versus RPM. I think if you had one between the drive and the transmission, it would just slip a whole bunch and be heavy.

I'd put my money on an elastic coupler or a wet clutch with a pre-defined breakaway torque.

You're not only trying to limit torque input from the engine, but also you need to protect from the momentum of the flywheel and transmission whizzing around. If you're in the air and you zing the engines, only to throttle back right before the prop hits, you still have 5000 rpm of spinning driveline that will impart torque to the drive even without the engine adding any torque. The torque imparted by momentum could be extremely high, theoretically only limited by prop slip.

With a clutch or an elastic coupler placed right before the input of the drive, you'd protect the drive from the flywheel and transmission momentum. Even a simple shear pin, while inconvenient, would be a good way to limit the torque being transmitted through the drive in an overload situation.

Randy

OK, is it just coincidence that there is an ad for fluid couplings under this thread:evilb:
Well there was a minute ago, I guess it changes!

It was one page back.:boat::)

http://www.turboresearch.com/fluid_d...uid_drives.asp

Or maybe it was this one.
http://kraftpower.com/powertran.html...FQMmbAodi35q5g

It was the first link. Very interesting that it showed up at the bottom of this thread. They aren't even marine products:et:.

The ads at the bottom are context driven. They search the words in the thread & serve up related ads.

Watch it... you'll get us an add for Man-Ass:angry-smiley-038:

I know this is an old thread, but I just stumbled upon it today. When we first started racing Bravo's they were very fragile but offered a performance advantage, so we ran them.
We determined rubber props absolutely extended drive life.
The problem was hub failures.

If you can find an advertisement for Mach props. you can see they had a great solution that would work today called the Mach lock.

Bart Garbrecht is in Lakeland Fl he may still hold the patent rights. I wish it would be implemented by Hering it could save some Bravo's. The cool thing about Mach Lock was that if the hub failed it became a solid hub.
Steve