Prop thrust question - needed for homemade engine design

I'm making a long tail outboard motor using a diesel engine and I'm trying to determine roughly the thrust the prop will be generating. Any help would be greatly appreciated.

The prop is a 7.75" diameter, 6" pitch prop (cupped).

The engine is turns at 3600rpm max. The boat it will be pushing will be a metal boat shaped like a dugout canoe and I'm guessing it will travel at 8-10mph.

The reason this is important is I'm considering connecting the long drive shaft (which will have the prop on the far end) directly to the crankshaft of the motor which will impart the thrust generated by the propeller to the crankshaft of the motor. The motor is rated to take 287.7 LBS of axial thrust. That's the magic number. If my prop is going to generator less than 287.7 LBS of thrust I can skip the thrust bearing.

I've seen photos of motors that are the same general design as what I'm building, they take any old motor and slap a drive shaft and prop on it, and it appears without any additional external thrust bearing. It appears they let the engine's crank shaft take the thrust.

Any input you could give me would be greatly appreciated. I'd like to know how much thrust the prop should develop and if I might exceed that magic number of 287.7 LBS.

Thanks!
You can see the motor at http://gregihnen.me, then under about me and my motor.
Greg Ihnen

Re: Prop thrust question - needed for homemade engine design

I can see why you're worried about thrust. That much force pushing forward on the crank will be hard on the seals for sure. Have you thought about the fact that you are also messing with the balance of the engine? A directly coupled shaft and prop will need to be balanced to the engine much like a vibration damper is balanced. A thrust bearing would lessen the critical nature of the balance. A CV joint might be an option also.