This repair manual covers MerCruiser marine engines manufactured between 1978 and 1984. It is designed for a range of 4-cylinder, Inline 6 (L6), and V8 engine configurations, including specific models such as MCM 120, MCM 140, MCM 165, MCM 470, MCM 485, MCM 898, MCM 228, MCM 260, MCM 330, MCM 370/400, and various Cyclone and Turbo variants, as well as MIE models. This manual provides detailed information for the repair and maintenance of these robust marine powerplants, emphasizing their engineering and reliability for optimal performance on the water. The purpose of this comprehensive repair manual is to serve as an authoritative guide for both professional technicians and experienced DIY mechanics. It details essential procedures including part removal, disassembly, cleaning, assembly, installation, and troubleshooting. With extensive diagrams, illustrations, and technical specifications, this manual aims to empower users to effectively maintain and repair their MerCruiser engines, ensuring longevity and operational efficiency. Safety recommendations are integrated to guide users through complex tasks, stressing the importance of using this manual for all service requirements.