Correct, it's a VM Motori block. It was known as a BMW tunnel bore because the crankshaft is inside the crankcase. Mercury sold them in the US for a few years before forming an alliance with Cummins. Hino also used the same block, and some parts are interchangeable. Parts are very hard to get. I had a 200hp version in an Albin 28. The air filter was interchangeable with a Yugo. I tried to get a new heat exchanger. The only factory bolt on heat exchanger I could find was used, and the seller wanted $6000 and that was about 7 years ago. At 1400 hours the engine ate a valve (ause unknown), and it took months to find parts (new head, valves, cylinder liner, pistons). I suspect if you need a major service you'll have to replace the engine, although at the time Mercury had one short block in their parts warehouse. I have a Camano now and love it, but if it had a BMW Tunnel Bore I would have stayed clear.