This workshop service manual covers the Mercury Mariner outboard engine, specifically models from 2000 to 2005 featuring the Optimax Direct Fuel Injection (DFI) system. These engines are engineered for reliable performance, delivering 175 horsepower with advanced DFI technology and electronic ignition for efficient operation. Designed for marine applications, the water-cooled engine system and standard outboard gearcase with forward, neutral, and reverse are built for durability and optimal power transfer in various water conditions. The purpose of this comprehensive English-language manual is to provide detailed guidance for the repair and overhaul of the Mercury Mariner 175 HP DFI Optimax Outboard. It covers essential maintenance procedures, troubleshooting common issues, and presents technical specifications necessary for effective servicing. This resource is intended for owners, mechanics, and technicians with basic mechanical knowledge, enabling them to maintain the engine's optimal performance and longevity.