I can't speak to current BMW Marine diesels but I sure can back up what C lectric said.
I had 2 pairs of the gas BMW's in the 80's. A pair of 180's that failed and I replaced with a pair of 220's.
They did a marvelous job of marketing and at the time, a local builder was offering them as an option. I think there were 7 of us who went for the 180's.
They were awesome packages coupled with the BMW Z-Drives. Quietest, smoothest engines I ever ran and easy to work on as far as regular maintenance. The legs and shifting were also smooth and a joy to use.
So,what happened?
As I recall, sometime around the 300 or 400 hour mark, the OH cams distorted enough to slam a valve into the top of a piston. About the same time, prop shaft seals started to fail and we had strawberry shakes in our out drives.
BMW did a ton of warrantee work on them, but only after they could no longer blame operator abuse. Mine was one of the catastrophes. They blamed a bad batch of cams and assured everyone all was well. They replaced one of my engines under warrantee.The second one was beyond just a new cam so they agreed to settle on it as well. I opted to pay the difference and upgraded to 220's.
There was one other failure ahead of me and the rest were about to crash as well and this was a tiny market. Everybody got at least new cams and prop shafts.
When the second batch of cams and prop seals started failing, they had no excuses other than "maybe they could not withstand the constant high revs." and we should all just slow down.???
By this time Merc had taken over and they would not do anything for anyone. Some folks repowered and some of us just took the bath.
One of the biggest problems was lack of BMW marine techs and nobody else would touch them. I would be suspect of that now as well, especially away from major centers.
It was a long time ago and they were gas I/O but I would not go anywhere near them again.
Ever!