This manual covers Mercury Mercruiser GM V8 engines, specifically models MCM 454 Mag MPI, MCM 502 Mag MPI, MIE 454 Mag MPI Horizon, MIE 8.2L MPI, MCM 7.4L MPI, and MIE 7.4L MPI. These V-8 engines, available in 7.4L (454 ci) and 8.2L (502 ci) displacements, are designed for reliable marine performance. This service and repair manual provides comprehensive information for maintaining and servicing these powerful engines. The purpose of this English-language manual is to assist DIY and professional mechanics in understanding and performing repairs. It includes detailed instructions and illustrations for general information, maintenance, troubleshooting, engine removal and installation, and various systems such as starting, ignition, charging, instrumentation, fuel injection, cooling, exhaust, drives, transmission, and power steering. This resource is designed to facilitate inexpensive repair and maintenance, ensuring the longevity and optimal performance of your Mercury Mercruiser engine.