This service repair manual covers marine diesel engines, specifically the 1GM10(C), 2GM20(F)(C), 3GM30(F)(C), and 3HM35(F)(C) models. Engineered for marine propulsion, these reliable diesel engines are designed to provide consistent performance in demanding maritime environments. Engines are recognized for their robust construction and efficient operation, making them a trusted choice for boat owners and operators. This manual provides comprehensive guidance for the maintenance, repair, and troubleshooting of your marine diesel engine. It includes detailed procedures, technical specifications, and essential safety information to ensure the longevity and optimal performance of your equipment. Whether you are a boat owner performing routine maintenance or a professional technician undertaking complex repairs, this manual serves as an indispensable resource for all aspects of engine care.