This workshop service repair manual covers the Mercury Mariner Marathon outboard engine, a robust 2-stroke, water-cooled unit producing 25 horsepower. Engineered for reliability and performance, this engine features a 470cc displacement, a 68 x 64 mm bore and stroke, and a CDI ignition system. Its fuel induction is managed by a carburetor, requiring unleaded gasoline mixed with oil at a 50:1 ratio. The transmission offers Forward-Neutral-Reverse with a 2.15:1 gear ratio, and the electrical system includes a 10-amp alternator. This manual provides comprehensive information for owners and technicians alike. The purpose of this manual is to offer detailed guidance for the maintenance, repair, and servicing of your Mercury Mariner Marathon outboard engine. It encompasses essential procedures, technical specifications, troubleshooting advice, and safety precautions. Topics covered include lubrication, fuel system requirements, electrical system diagnostics, and performance-related components such as propeller selection. By following the instructions within this document, users can ensure optimal performance, longevity, and safe operation of their Mercury Mariner Marathon engine.