In a diesel engine closed fresh water cooling system, the cooling water pressure drop through the engine is 10 psig, and the pressure drop through the heat exchanger is 4 psig at maximum flow rates. The cooling water pump must produce a discharge head of at least __________.

Correct Answer: Option C — 15 psig

Total pump discharge head must overcome the combined hydraulic resistance of all system components. Adding the 10 psig pressure drop through the engine to the 4 psig drop through the heat exchanger yields a minimum required pump differential pressure of 14 psig, rounded to 15 psig.