Re: no forward
Hippie, I'm confused....you say " I can not see how how this thing fits in snug the way you are describing, there are no groves are anything on either the prop or the shaft"
I read up this thread and I don't see where anyone says that the shear pin (drive pin) should be snug....
I did see Paul's reply regarding the shift linkage and his suggestion , not to overtigtning the bolt.
As for the shear pin, the drive shaft turns, which drives the shear pin. Since the pin goes thru the prop, it too it turned with the shaft. The purpose of the drive pin (shear pin) is to protect the lower unit gears if an obstruction is hit by the prop. If the pin shears , you should have 3 pieces, one on either side of the prop, and a piece in the drive shaft hole. Remove all 3 pieces and replace with a new drive pin. Do Not substitute this drive pin with a nail. The drive pin is not a soft pin. Typically they are cast iron, designed to fracture at the drive shaft, thus 'shearing' the pin.
I'm assumming that since you had reverse, the broken pin ends were binding the prop just enough to make headway.
After re-reading your replies, you may not have had the linkage improperly adjusted, the reason for reverse only operation.
Newer motors can have splined drive shafts with mating splined prop hubs. There's ,of course, no need for a shear pin on these motors, the splines drive the prop. They do have a rubber inner prop hub that will 'spin' if an obstruction is hit. If this prop slips while under torque, the prop can be 're-hubbed" at a prop shop for a nominal fee.