I am amazed to learn that there are more narrowboats that have a Mercedes OM 636 engine, this was the first time I heard about one fitted in one.
They must be pretty rare anyway, as in all the years that I've been reading about narrowboats, and looking regulary through the ads, I've never seen one listed before.
Many years ago I had an old 1957 Mercedes 180D ex-taxi, that had done 500.000km when the car died, the engine was never overhauled and still running beautifully, it was bought by someone who was going to marinise her and put her in a boat, I wouldn't be surprised if she's still running.
Peter.