Re: 1300 hrs. on sailboat engine in 23 years??
My 23 yr. old boat has a Yanmar 3GM30F with about 1100 hrs and has never been chartered/ timeshared. The OP's boat of interest apparently was in a timeshare--not charter service--and has a reasonably low number of hours.
If that boat were in an active charter operation, it would likely be pretty worn out. Some of the boats I've chartered in the Caribbean showed 400 hrs/yr on the engines. I doubt you'd see that time in other venues.
You should expect to run a diesel easily past 6000 hours if it has been properly maintained.