This manual covers the Mercury Mariner outboard motor, specifically models from the 2002-2004 production years. These engines are part of the First Generation Optimax series, featuring a 3.0L Direct Fuel Injection (DFI) 2-stroke engine that delivers 250 HP. Engineered for reliability and performance, the Optimax system utilizes advanced fuel injection and oil delivery for efficient operation. This marine outboard motor is designed for a wide range of boating applications, offering robust power and dependable service. This comprehensive Service Repair Workshop Manual provides essential information for the maintenance, diagnosis, and repair of your Mercury Mariner outboard motor. It includes detailed step-by-step instructions, clear diagrams, illustrations, and wiring schematics to assist with all aspects of upkeep. Key areas covered include scheduled maintenance tasks such as oil and filter changes, spark plug replacement, and fuel system servicing, as well as troubleshooting guides for electrical, fuel, powerhead, cooling, and pump unit issues. This manual is an indispensable resource for owners, mechanics, and technicians seeking to ensure the optimal performance and longevity of their marine engine.