About five years ago I sea trialed a trawler with one of these engines. It was in rough shape. Turbo was seized from a leaky exhaust mixer, and some other problems. It ran ok (obviously only at lower power due to the turbo). Afterward I did a search to see what parts were available. I don't remember all the details but the conclusion was it was mostly an orphan. Lots of parts simply not available.
The guy ended up buying the boat with a discount and immediately repowered it with a Yanmar.
I would avoid buying a boat with this engine. It may run fine and be in good shape, but it is no fun knowing that you are one part failure away from some mad parts search or a forced repower.
Or get a discount and repower straight away. Or just keep a budget for a repower and run it as long as it keeps going.... Dilemma...