When transitioning from maneuvering speed to full sea speed on a slow-speed diesel-powered vessel that features a direct-drive fixed-pitch propeller propulsion arrangement, how should this be accomplished?

Correct Answer: Option B — The engine should be accelerated from maneuvering speed to at sea speed very gradually, but should transition through any critical speeds without any lingering.

Slow-speed diesel engines with fixed-pitch propellers often possess critical speed ranges where torsional vibrations are amplified. Accelerating gradually allows for steady operation, but the engine must transition through these critical ranges quickly to prevent prolonged exposure to high-stress vibrations that could cause mechanical fatigue or catastrophic shaft failure.