This manual covers the Mercury Mariner 40 Marathon, a 2-cylinder, 40 HP outboard engine designed for marine propulsion. This water-cooled, gasoline-powered unit features a CDI ignition system and an outboard gearcase with forward, neutral, and reverse gears. Its robust engineering is intended to provide reliable performance for a variety of boating applications, ensuring dependable operation on the water. This Factory Service Repair Manual, presented in English, provides comprehensive guidance for the maintenance and repair of your Mercury Mariner 40 Marathon. It details essential procedures including routine maintenance tasks such as oil changes and component replacements, along with technical specifications and troubleshooting information. This manual is an indispensable resource for owners, mechanics, and technicians seeking to preserve the optimal performance and longevity of the outboard engine.