The above is basicly correct... but not the full story.
The navy tend to put props on the other way around because props turning
inwards towards each other at the top is more efficient
This is done on the basis that navy ships have tugs etc to assist manouvers
in port.. so they trade the manouverability for better efficiency at speed.
When all is said and done, you will have to fit the props to suit the
engines/gearboxes as fitted to the boat unless you wanna swap them round

Add to this, most Navy surface combatants (not sure about carriers, though
doubt it) use variable pitch props, which throws in a whole other set of
handling characteristics .... some can do a credable twin screw

Shen