This service and repair manual covers Mercury Outboard Motors manufactured between 1965 and 1989, specifically focusing on 2-stroke engines within the 40-115 HP range. These robust outboard motors are known for their reliable performance on the water, making them a popular choice for various boating applications. This manual provides comprehensive information to ensure these engines continue to operate efficiently. The purpose of this manual is to provide detailed guidance for both do-it-yourself enthusiasts and experienced mechanics. It includes step-by-step instructions, supported by numerous photos and illustrations, covering all aspects of maintenance and repair. Key areas addressed include general maintenance schedules, lubrication, troubleshooting common issues across the electrical system, fuel, ignition, power head, and gearcase, as well as detailed procedures for component disassembly and reassembly. Wiring diagrams are also included to aid in electrical system service.