The Mercury Mariner Marathon is a robust outboard engine designed for reliable performance. This 25 horsepower, 4-stroke, 2-cylinder engine features a 430cc (26.2 cubic inch) displacement and is water-cooled for efficient operation. It is equipped with a Forward-Neutral-Reverse gear system and a 2.15:1 gear ratio, suitable for a 20-inch long shaft. The Mariner Marathon is engineered for durability and consistent power output, making it a dependable choice for various marine applications. This Service Repair Manual provides comprehensive guidance for the Mercury Mariner Marathon outboard engine, covering serial numbers 0G044027 and Above (US) and 09807909 and Above (Belgium). It details essential maintenance procedures, including lubrication requirements for the gearcase and engine oil, spark plug specifications, and fuel system recommendations. Technical specifications, troubleshooting steps, and safety guidelines are also included to assist owners and technicians in maintaining the engine's optimal performance and longevity.