Wow thats tight! Way to much work...
I'm pondering... pull the set screw on the shaft, tie a rope
to the prop and slip the shaft back enough to pull the coupler. Would have to align it, sounds like you gotta do that no matter what, but doing the socket between the halves and tightening up the bolts is a lot easier than pulling the engine
(I'd be tempted to knock in a plug
and hop back onto the dock
shaft in hand screaming "It just fell
How long is the hose coming off the shaft tube/shaft log, or is it all one casting?
If you can get the shalt half of the coupling off, I'd drop it off at a machine shop and have them take a little off the shaft side to gain some space (given the prop doesn't slide forward and hit anything.) 1/8th inch off the shaft side of the coupler would be 3.175mm.
(I wouldn't take off the transmission
side of the coupling. Had the nut that holds that one on, fall off. Not going anywhere when that happens!)
While your at it laying the flat side of the nut on a belt sander until it looks a little thicker than to thin...