Question 70 ONC05 - Master or Mate of LT 200 GRT

The Correct Answer is D. **Why option D ("Decrease your engine speed") is correct:** When a propeller is "racing," it means the propeller is briefly coming out of the water (ventilating or broaching) due to rough seas, losing its load, and spinning much faster than normal. This rapid acceleration causes severe stress and potential damage to the engine, propeller shaft, and gearbox (a phenomenon known as "shock loading"). To prevent damage and regain control, the immediate action must be to reduce engine speed (throttle back). Decreasing the engine speed ensures that when the propeller re-enters the water, the shock loading is minimized, and the engine's RPM remains within safe limits. This action helps maintain control and protects the machinery. **Why the other options are incorrect:** * **A) Ignore it, this is acceptable in rough weather:** This is dangerously incorrect. Propeller racing subjects the propulsion system to extreme mechanical stress and can lead to immediate equipment failure (e.g., bent shafts, cracked couplings, or catastrophic engine damage). It must never be ignored. * **B) Increase your engine speed:** Increasing speed exacerbates the problem. If the propeller is already racing out of control, applying more throttle will cause it to spin even faster when it next breaches the water, drastically increasing the risk of catastrophic engine and drivetrain damage. * **C) Stop your engine until the rough weather passes:** While stopping the engine eliminates the risk of racing, it sacrifices all maneuverability and propulsion control, putting the vessel and crew at greater risk in rough weather. The goal is to safely continue operating the vessel, not stop it completely. The correct preventative measure is throttling back, not shutting down.