This manual covers the Mercury Mariner 225/250 HP EFI Outboard, a powerful and reliable marine engine designed for demanding applications. Engineered with advanced Electronic Fuel Injection (EFI) and robust internal components, these outboards deliver exceptional performance and efficiency. The comprehensive coverage of engine management systems, ignition, and fuel systems ensures optimal operation and longevity for a wide range of model years. This Factory Service Repair Manual provides essential information for maintaining and repairing your Mercury Mariner outboard. It includes detailed step-by-step maintenance procedures, advanced diagnostic and troubleshooting guides, and common fixes for owner guidance. Technical specifications, wiring diagrams, and coverage of critical systems such as charging, starting, and oil injection are thoroughly explained, empowering owners and technicians to keep the engine in peak condition.