Many years ago, my first job out of college was working for a shipyard. At the time we had a ship under construction with a 12 cylinder Sulzer diesel engine about the size of the one in the picture. The block was so big that there was a full sized door in the side for entry and there were walkways...inside the engine.
It was 167 feet long. I remember inspecting the exhaust manifold expansion joints. From inside the exhaust manifold. I could stand up fully erect inside the exhaust manifold.
Each of the 12 cylinders had a bore of something on the order of 1 meter (it's been 25 years I don't remember the specifics).
The rotation speed of the engine was such that it didn't require a gearbox and was directly coupled to the 40 foot diameter propeller. It rotated about 50 rpm if memory serves me correct. To go backwards the engine was turned off, the cam gear shifted and the engine was started in the opposite direction.
I didn't realize these things were still made.
chris