This manual covers Mercury 2-stroke outboard motors manufactured between 1965 and 1989, designed for marine propulsion. These engines, available in various horsepower ratings from 90 HP to 300 HP and featuring a 3.4L displacement, represent a robust and reliable choice for boaters. The engineering quality inherent in these Mercury outboards ensures dependable performance for a wide range of aquatic activities. This comprehensive document serves as an essential resource, encompassing repair, service, and owner's information. It details routine maintenance procedures, engine specifications, fuel and lubrication systems, electrical diagnostics, and advanced troubleshooting techniques. By providing clear instructions and technical data, this manual empowers owners and technicians to effectively maintain, repair, and optimize the performance of their Mercury outboard motors.