Get a good local cat mechanic to ride with you on a sea trial with clean prop and bottom. A good cat guy will know what to check. Blowby flow, rpms, boost and temps at full, oil samples to look for salt entry, alt volts, exhaust layout ok, visual insp, etc. He should have his own checklist.
Lots of folks poo-poo that engine, but in trawler service and run properly, it is a very nice machine IMO.