This workshop service manual covers the Mercury Mariner 25 BigFoot outboard engine manufactured between 1998 and 2008. Designed as a reliable 4-stroke, water-cooled engine, the Mariner 25 BigFoot delivers 25 horsepower, making it suitable for a variety of boating applications. Its engineering prioritizes durability and consistent performance, with the BigFoot designation indicating a specialized lower unit designed for enhanced torque, ideal for heavier loads or specific hull types. This manual provides comprehensive information to ensure the optimal operation and longevity of your Mercury Mariner outboard. The purpose of this manual is to serve as a definitive guide for owners, technicians, and mechanics. It details essential maintenance procedures, including lubrication and recommended service intervals, alongside troubleshooting guidance to address potential issues. Technical specifications, such as engine configuration, cooling system details, and transmission information, are thoroughly explained. Safety guidelines are also integrated throughout the document to promote responsible operation and maintenance. By following the instructions within this manual, users can effectively maintain, service, and repair their Mercury Mariner 25 BigFoot engine.