While at sea, the first engineer reports the jacket water expansion tank water has become discolored and has a smell of exhaust on a slow speed two stroke engine. Which would be the most likely cause?

Correct Answer: Option A — A cracked cylinder liner, cylinder head or exhaust valve cage

Combustion gas contamination and exhaust odor in the jacket water expansion tank indicate high-pressure combustion gases escaping through a crack in a cylinder liner, cylinder head, or exhaust valve cage directly into the cooling water jacket.