View Full Version : Universsal joints for inboard

02-03-2009, 04:37 PM
"I am trying to come up with a way to install an 8 hp air cooled inboard in a fishing skiff. Space limitations, etc. dictate that the engine must be installed level, i.e. I cannot tilt it down on the back end to meet the prop shaft comming through the bottom of the boat, the shaft obviously being at an angle off of horizontal.

So, can I mate the engine to the propshaft by the use of a universal joint, same as in an auto drivewhaft. I have never seen this done, but It seems like it outght to work. Am I missing something??

If a u-joint won't work, how about a Constant Velocity joint?? Where might I get one of this size?? Obviously, an automotive one would be way overkill and might eat up all 8 hp in friction losses.

Engine is a Honda commercial air cooled, 8HP at 3600 rpm (direct drive, no gear but with a centrifical clutch),plan on cruising at approx 2600, pushing an 18 ft. wooden fishing shiff that weighs approx 500 lbs.

Finally, anyone know of a v drive suitable for an 8 hp motor??

Thanks ever so much"

02-03-2009, 05:10 PM
Go for it. Mercruiser has been using u joints since forever in their outdrives. OMC before u joints used a ball gear setup. If you have a way to mate the two shafts and keep them in balance and greased.

02-03-2009, 05:23 PM
"Why not try a universal joint from a smaller lawn tractor. It would certainly handle 8 hp. I believe that John Deere still has the ones with grease fittings, which would be handy. I would make sure you had a rather easy disconnect for replacing the universal without having to remove the engine."

02-03-2009, 06:51 PM

I'd go with a thrust bearing setup at the front end of the shaft. the commercial ones I've seen use CV joints as they are a bit more robust in a flexing environment. Make sure you have a good ventilation plan for that engine, the load a boat puts on them is significant."

02-04-2009, 12:08 AM
"I think Mako hit the point, but I would go with a CV joint of some sort due to its ability to absorb some telescopic flexing that would otherwise knock the #*@% out of your driveline.

Suggest leaving the doghouse open as air cooled is air cooled... as you know. Sounds like a fun project."