If you need a new shaft and don't want to replace it, this is for you.
A previous owner of my boat
did this. The only reason I can think of was he didn't want to replace the shaft.
1. The orig. 1" shaft was turned down to 7/8"
2. The coupler had a bushing welded into it (for the 7/8 shaft) and a new keyway cut.
3. Replaced the 1" stuffing box with a 7/8" one
4. Put a plastic bushing in the prop bore to compensate for the smaller shaft.
I discovered it when replacing the stuffing box , to shaft log rubber hose. I couldn't get a hoes that would fit the log, and the, now smaller dia. stuffing box.
I changed it all back to 1", as I needed a shaft anyway.