As a general rule, what would be the recommended operating water jacket outlet temperature range for medium-speed marine diesels setup with closed treated fresh water cooling systems and fitted with vented expansion tanks?

Correct Answer: Option C — 165° to 180°F

Medium-speed marine diesels operating with closed treated fresh water cooling systems typically maintain a jacket water outlet temperature between 165°F and 180°F to optimize thermal efficiency, ensure proper oil film retention, and minimize corrosive acid condensation.