What is the function of the turning gear when a ship is docked?

The turning gear's primary function when a ship is docked is to rotate the main engine gears while the engine is not operating at full power. This action helps maintain lubrication and prevents wear by ensuring that the gears and associated machinery do not seize up. It is especially critical when the ship is idle for extended periods, allowing for the even distribution of lubricants throughout the system. This is crucial in maintaining the readiness of the machinery for future operation.

The other choices do not accurately reflect the function of the turning gear. While increasing fuel efficiency and securing all engine operations may be important, they are not direct purposes of the turning gear. Likewise, powering auxiliary systems does not pertain to the primary role of the turning gear, which is specifically associated with the operational status of the main engine's components.