Propeller shaft pulls out of the transmission collar

[Charles Akins]

I have downloaded and printed the HURTH transmission manual. Unfortunately, my problems start just south of where the manual ends.
The drive shaft attaches to the prop with a collar that is bolted to a matching collar on the transmission by four bolts. The stern collar has two set bolts that attach the propeller shaft to the collar. One bolt has a square head and the larger one has a hex head. One bolt holds a key into a keyway in the propeller shaft-collar. The other bolt is apparently the friction attachment for the shaft to the collar. My problem is the shaft pulls out of the collar when the transmission is shifted into reverse.
I have several questions about this system:
Which bolt is supposed to hold the key in the keyway small square head or larger hex head? I would think the square head is for the key. Is that correct?
Does the non-keyway bolt just produce a friction fit or should it fit into some kind of notch/hole/grove on the shaft?
Is anything other than friction from the set-bolt on the key-keyway to keep the shaft from being pulled out of the flange when the transmission is in reverse? That seems like a rather week attachment to hold 40 HP engine.
Is the key soft to act like a shear pin or will any ¼ inch key work?

Thanks for the help!

Charles Akins

[Don Moyer]

Charles,

You apparently have a Universal diesel, but the prop shaft coupling arrangement is much the same as on an Atomic 4 powered boat. The set screw over the keyway is usually not the set screw that prevents the shaft from pulling out of the coupling while in reverse. The set screw that is 90 degrees from the keyway should have a dimple in the shaft for the end of the set screw to seat into.

Don

[Charles Akins]

Thanks!

It is an Atomic 4, not a diesel.
I don't trust anything without a carburetor and spark plugs.

Charles Akins