My Shaft coupler was a rusty mess, with no discernable bolt heads or set screws, and there is not enough room along the shaft between the back of the motor and the stern tube to repack the stuffing box without removing the coupler. I don't believe the packing has been changed since the '73 Atomic four motor was rebuilt in 1989.

So ... over the past two weekends I sliced off the shaft coupler with an angle grinder and dremel, and was able to drill out the 3 bolts remaining in the output coupler. I can now repack the stuffing box, and will change the cutlass bearing as well. I am also replacing the stuffing box with shorter parts so that I could hopefully change the packing without removing anything. .