The water guide jacket, code P50507-03, plays a vital role in the thermal management of the MAN L21/31 engine by channeling coolant around critical engine components, such as the cylinder liners and combustion chamber. It ensures even heat distribution, prevents hotspots, and supports optimal engine temperature during operation. Constructed from corrosion-resistant materials, the jacket helps extend the life of internal parts and safeguards the engine against overheating, making it indispensable for sustained high-performance use at sea or in power plant conditions.