steam engine, or steam turbine low, perhaps 20% .
Are you asking about the old fashioned paddle wheels, which were steam driven (hence the name steam boat), and later propellers were steam driven. Now electric generators can be steam driven, as in nuclear powered vessels. John seems to have summarized that pretty well.
The efficiency of large steam powered vessels gets pretty high, as high as 35-40 percent from what I remember about naval vessels.
Many modern ships are powered with electric motors. The electric generators are sometimes powered by steam driven turbines, sometimes gas turbines. Some ships have propulsion driven directly with steam turbines. -- Regards, John Popelish
