This comprehensive service and repair manual covers the Mercury Mercruiser 8.1L 496CID engine, specifically models #30. The manual details both sterndrive (MCM) and inboard (MIE) configurations, encompassing the 496 Mag HO and 496 Mag sterndrive models, as well as the 8.1S HO and 8.1S Horizon inboard models. It provides extensive information on troubleshooting, maintenance, and repair procedures for this powerful petrol engine. The manual delves into a wide range of topics, including engine removal and installation, starting, ignition, charging, fuel systems, fuel injection, cooling, exhaust, exhaust manifolds/elbows, as well as transmissions including Velvet Drive and Hurth, and power steering systems. Each section features detailed illustrations, step-by-step instructions, and clear diagrams to guide you through every process. The manual serves as an invaluable resource for both novice and experienced mechanics, enabling you to perform maintenance and repairs efficiently and effectively.