[zappo2938]

Maybe not. Marine diesel engines can run without the computers attached using mechanical throttles. There has been instances where the yacht's wheelhouse is flooded with water and all the navigation computers and electronic controls are lost. The captain and mate stationed in the engine room coordinate by controlling the manual throttles on each engine. Move one throttle more to turn.

[scrumper]

Depends on the ship of course, but this wouldn't have worked on at least one of the naval vessels I've visited. Common on newer ships are electric drives, where diesel or gas turbine engines are connected to generators instead of prop shafts.