SUNBEAM is motoring away from a mooring when there is a sudden bang, the engine note changes, and the boat slows right down even though the throttle is still open. What is the most likely cause?

A. This always means the engine has suffered a major internal failure needing a full rebuild

B. This pattern always means the fuel has run out completely

C. A sudden bang and slowdown like this is completely normal and needs no investigation

D. A rope, mooring line, or fender line has almost certainly wrapped around the propeller, jamming it or stalling the engine — this is one of the most common causes of a sudden loss of drive with this exact pattern of symptoms

A. Increase engine revs to try to cut through the rope with propeller speed

B. Ignore the engine entirely and focus only on the boat's position for several minutes

C. Put the engine into neutral and switch it off straight away — continuing to run the engine winds the rope tighter around the shaft and propeller, making the problem worse and risking damage to the shaft seal, stern gland, or gearbox

D. Keep the throttle open and try repeatedly going forward and reverse to "shake" the rope free

A. Wait passively with no plan, regardless of what the boat might drift into

B. Immediately jump into the water to deal with the rope before checking anything else about the boat's safety

C. Check the boat's position and what it is drifting towards — is there enough room and time before reaching a hazard such as other moored boats, rocks, or the shore? If there is any danger, consider using sails (if there is wind) or the anchor to regain control

D. Assume drifting is never a problem regardless of what is nearby