I am aware that some large military ships are powered by gas turbine engines, and others are powered by gigantic diesel engines. For civilian ships, I’ve only ever heard of diesels. Are there any powered by gas turbines?
How is the choice made between one or the other during the design phase?
Mostly diesel engines now says. A few gas turbines. The choice would be 1st fuel efficiency. 2nd cost. 3rd labor. 4th repair and maintenance cost. Also in there would be room required and auxillary machinery. A gas turbine would also require a gear reduction or generator and motor set.
Short answer is cost. Gas turbines have a size & weight advantage but diesel is lower cost in general.
Diesel Engines and Gas Turbines in Cruise Vessel Propulsion (pdf)
There are also steam turbine powerplants - some fueled by petroleum products, and some by nuclear reactors.
Gas turbines (pretty much just a big jet engine) are the powerplant of choice for high speed passenger catamarans. i.e. where speed really matters and can be a selling point.
For most marine freight the important thing is how cheaply rather than how quick.
An answer in 52 minutes.
Fifty-two minutes???
Slacker.
They are not building steam ship for the merchant Marine the days. Takes too much fuel.