This workshop service manual covers the Mercury Mariner outboard motor, specifically the DFI Optimax generation produced between 2000 and 2005. This V6 engine, displacing 2.5 liters and producing 135 horsepower, features Direct Fuel Injection and a CDI ignition system with Electronic Spark Advance. Its robust engineering ensures reliable performance for a wide range of marine applications. The manual provides comprehensive details on its specifications, including bore and stroke, gear ratio, and shaft length, offering insights into its powerful and efficient design. This comprehensive English-language manual is designed to assist owners, technicians, and mechanics in maintaining and repairing their Mercury Mariner outboard motors. It details essential maintenance procedures, such as recommended oil types, spark plug gap settings, and fuel octane requirements, alongside troubleshooting guidance and technical specifications. By following the instructions within this manual, users can ensure the longevity, optimal performance, and safety of their DFI Optimax engine.