In the 1980's, I performed a 2 week Naval Reserve Exercise aboard a Danish Built Merchant ship which had a 7 cylinder 35,000 hp Fiat built Diesel. It ran at 95 RPM Maximum and idled at 35 RPM. To Back the ship down, there was no clutch material that would hold up so the process was to stop the engine and reverse the engine itself. It ran as well in either direction. It would start on Diesel and warm up then would be shifted to Bunker "C" fuel which was nearly crude oil. It had to be shifted back to diesel and run at full power for 2 - 4 hours before bringing it to port and shutting it down. Everything wa computerized. The Aluminum pistons weighted 2,500 lbs and you could stand in the cylinders. The crankcase had huge hinged doors to access the lower end. Quite impressive and it worked well for a point to point vessel. You could disconnect a cylinder and run on 6 or 30,000 HP. I'm sure there are bigger one out there. This ship was around 35,000 tons gross registered tonnage and 650' long. It was part of the Maritime Prepositioning Force in Diego Garcia, an island 1,000 miles south of India.
A great experience.