Okay one of the few pictures i can find that gives you some sence of scale.

That is a 2 stroke made by a company called B&W the 90 refers to piston size (900mm)

Puts out about 4600Kw per clyinder and revs about 70rpm

Features varable timed injection, hydraulic opened exhaust valves with compressed air springs, and huge turbos.

And currently in development by all the major engine manufactures are intelligent engines with no camshafts everything completely computer controlled.

They truely are amasing engines as nothing is wasted. The cooling water is used for making fresh water from sea water and the exhaust gas is used to heat water to make steam for heating. There is even engines out there that use excess exhaust pressure to drive a turbine coupled into the prop shaft to give an extra shove