This service and repair manual covers Mercury Outboard motors, specifically 45-115 HP 3 & 4 Cylinder 2 Stroke models produced between 1965 and 1989. These engines are known for their robust construction and reliable performance, making them a popular choice for various marine applications. This manual provides comprehensive information to ensure these engines continue to operate at peak efficiency. The purpose of this manual is to provide detailed guidance for the maintenance, troubleshooting, and repair of your Mercury Outboard motor. It includes essential information on tune-ups, scheduled maintenance, engine oil type guidance, coolant changes, and detailed procedures for rebuilding the powerhead and repairing the lower unit. Furthermore, it covers the electrical system, fuel system, controls, and starting system, along with technical specifications, torque values, part diagrams, and troubleshooting guides. This resource is designed for owners, mechanics, and technicians seeking to maintain and repair these engines effectively.