When changing over from residual to distillate fuel on a slow-speed diesel propelled vessel, you should limit the rate of temperature change of the fuel in order to prevent what operational difficulty?

Correct Answer: Option A — Seizing and scuffing of fuel pump plungers and injector needle valves due to thermal effects on close clearance components.

Rapid temperature shifts during fuel changeovers cause uneven thermal contraction between close-tolerance pump plungers, barrels, and injector needle valves. Limiting the cooling rate prevents differential thermal distortion that leads to immediate seizing and scuffing.