Before opening the inspection cover of an engine, what is the necessary condition?

The correct answer highlights the importance of ensuring the engine is cooled down before opening the inspection cover. After engine operation, temperatures can rise significantly, creating potential safety hazards. A hot engine can lead to exposure to burns from hot surfaces or fluids, and it may also create a risk of thermal expansion that could affect the integrity of the components.

Cooling down the engine allows technicians to work safely and effectively, reducing the risk of injury. Therefore, that condition is essential for safe operation and maintenance practices on marine engines.

Regarding the other options, while having an empty fuel tank or having changed the oil could contribute to safety in different scenarios, they do not directly pertain to the immediate risks posed by a hot engine at the time of inspection cover opening. Additionally, if the engine is running, it poses a greater danger due to moving parts and the risk of hot surfaces. Thus, focusing on cooling down the engine directly addresses critical safety concerns.