Starting large marine diesels is a readiness problem

How long did it take to start the marine diesels of ships such as the Deutschland class?

The engines may start quickly, but preparing the associated systems can take a couple of hours or more.

The reply separates cranking a diesel from making an entire warship propulsion plant ready. The engine itself can start in minutes once the correct conditions exist. Heating, lubrication, electrical supply, auxiliaries, and associated machinery may need hours of preparation from a cold state. A Deutschland-class ship held at a higher readiness could shorten the process, but a couple of hours is a better operational estimate than the time needed merely to turn over the engine.