This Service & Repair Manual covers Mercury 4-Stroke Outboard engines, specifically the 40, 45, and 50 horsepower models, including the 50 Bigfoot variation. These water-cooled engines, equipped with electric start and a CDI ignition system, are designed for reliable performance. The Bigfoot designation signifies a lower gear ratio, enhancing torque for applications requiring increased pulling power. This manual is applicable to units starting with serial number 0G231123. This comprehensive manual provides detailed information essential for the maintenance and repair of your Mercury outboard. It includes in-depth coverage of critical systems such as the electrical, fuel, powerhead, mid-section, and gear housing. You will find instructions on lubrication, fuel system requirements, and recommended spark plug types. The manual also details the shift sequence and trim/tilt systems, serving as an indispensable resource for owners, mechanics, and technicians to ensure the longevity and optimal performance of their Mercury engine.