One major disadvantage of a low-speed diesel as compared to a steam main-propulsion system is __________.

Correct Answer: Option B — a minimum speed for the engines that limits the minimum speed of the vessel

Low-speed direct-drive diesel engines have a minimum stable operating RPM. Unlike steam turbines, which can operate at very low speeds, a direct-drive diesel's minimum speed is constrained by the engine's combustion stability and mechanical limitations, which in turn dictates the minimum speed at which the vessel can safely maneuver.