Which of the following procedures should be carried out to permit the continued operation of a crosshead engine with a leaky aftercooler?

Correct Answer: Option D — Blank off the cooling water lines and run at reduced speed.

A leaking aftercooler allows raw water to enter the air intake, risking severe water hammer or scavenge fire. Blanking off the water lines stops raw water entry, while operating at reduced speed maintains propulsion safely until permanent repairs are made.