At first blush, it sounded like a lot of time. But breaking it down as follows maybe not a lot of waste.
First it would require 2 workers to get the prop shaft and strut off the boat and reinstalled.
2 workers at 6 hours a day say 3.5 days that is 42 hours. The work on the shaft and coupler will be mechanical shop time at least 3 hours. That leaves about 8 hours if something goes wrong, then there is the fiberglass plus fairing work and bottom painting to do. Will there be a supervisor checking the workers being sure they install the PSS correctly this time? Important that they replace the set screws with new ones on the PSS collar.
It is not like the auto shop that has a book of hours it takes to do a specific job that they use for estimating a job.
Good luck. Stick around the yard and observe the job. Maybe you’ll get into the work and think I can do that.