In the open cooling system, how is the engine cooled?

• A. Directly by sea water
• B. By a closed-loop antifreeze
• C. By air cooling fins only
• D. By oil cooling only

Answer: (A)

In an open cooling system, the engine is cooled directly by seawater. A seawater pump pushes seawater into the engine where it circulates through the cooling passages, absorbing heat from the engine, and then is discharged overboard. Since the cooling medium is sea water and it isn’t recirculated through a separate closed loop, there’s no antifreeze-filled loop involved. This is different from a closed-loop system, which uses a separate antifreeze coolant and a heat exchanger. The other options don’t fit because air cooling fins don’t apply to open-water cooled engines, and oil cooling alone isn’t how the engine is kept within proper temperatures in this setup.