As a general rule, what would be the recommended operating water jacket outlet temperature range for medium speed marine diesels set up with closed treated fresh water cooling systems and fitted with vented expansion tanks?
Official USCG Answer & Rule Citation
Correct Answer: Option D — 165° to 180°F
Closed freshwater systems on medium speed diesels operate best within 165°F to 180°F to ensure proper combustion chamber temperatures and prevent thermal fatigue.
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