This manual covers the Westerbeke 55A FOUR Marine Diesel, a robust 4-cylinder, 4-stroke, water-cooled diesel engine designed for marine applications. With a displacement of 2.18L, this engine is engineered for reliability and performance in demanding maritime environments. Its comprehensive design includes key components such as the cylinder head, valves, gearcase, oil pump, timing gears, camshaft, crankshaft, piston, connecting rod, fuel system, governor system, glow plug system, cooling system, starter system, and alternator system, all built to Westerbeke's high standards. This comprehensive workshop and service manual provides detailed information essential for the maintenance, repair, and operation of the Westerbeke 55A FOUR Marine Diesel. It includes step-by-step instructions, detailed illustrations, and diagrams for procedures such as engine overhaul, disassembly, and service of the fuel, cooling, starter, and alternator systems. Troubleshooting guidance and technical data, including tightening torques, are also included, ensuring that owners, mechanics, and technicians have the necessary resources to keep the engine in optimal condition.