And you thought a TO4 was big..The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today. The Aioi Works of Japan's Diesel United, Ltd built the first engines and is where some of these pictures were taken.
from here: http://www.msc.navy.mil/n7/newsltr/v01_i06.htm7. The last time I checked, the largest low speed marine diesel was the 12 cylinder Wartsila/Sulzer RTA96C. This monster puts out a whopping 89640 BHP (65880 kW) at 100 rpm. The bore, stroke, and mep respectively are 960 mm, 2500 mm, and 18.2 bar. The first ship to receive this engine was the large container ship NEDLLOYD SOUTHAMPTON.