Exhaust leaks would have nothing to do with hard starting (there is no exhaust till it is running). I wouldn't advise going to all that work to look at the shift rod boot unless you have good reason to suspect it. The indication for that would be smothering with the hood on but running OK with it off---on a boat, on the lake. Shucking that thing out of the shell is a major job.
I'd highly suspect the coils, if you haven't looked at them yet. They are well known to crack with age. Not limited to the 9.5hp, but all OMCs of the era.