This service manual covers the Mercury Mariner outboard motor, specifically the 40-45-50 Bigfoot series. These 4-stroke gasoline engines are water-cooled and designed for reliable performance. The Bigfoot designation indicates a larger gearcase, providing increased torque and durability, making these motors suitable for a variety of demanding marine applications. While specific production years are not detailed, the engineering quality inherent in Mercury outboards ensures dependable operation when properly maintained. This comprehensive service manual provides essential information for owners and mechanics. It details maintenance procedures, troubleshooting guides, and technical specifications necessary for the upkeep and repair of your Mercury Mariner outboard. With step-by-step instructions, hundreds of photos and illustrations, and clear notes on cautions and warnings, this manual aims to empower both do-it-yourself enthusiasts and experienced technicians to ensure optimal performance and longevity of the engine. The content is presented in English and is available in a digital, printable format.