This workshop service repair manual covers the Mercury Mariner outboard motor, specifically featuring the 3.0L Marathon gasoline engine. This water-cooled propulsion system is designed for marine applications and represents a robust engineering solution. While specific production years are not detailed, the manual focuses on the technical aspects of this engine variant, providing comprehensive information for its operation and upkeep. The purpose of this English-language manual is to serve as a complete official factory service resource. It includes detailed maintenance procedures, diagnostic steps, troubleshooting guides, and information on the electrical system. Owners, mechanics, and technicians will find the hundreds of pages within this document invaluable for understanding, maintaining, and repairing the Mercury Mariner 3.0L Marathon outboard motor, ensuring its continued performance and reliability.