This comprehensive repair manual provides detailed instructions and technical specifications for maintaining and repairing Yamaha 70HP and 90HP 2-stroke outboard motors manufactured between 1988 and 1994. It covers all versions of these models, encompassing a wide range of topics essential for both novice and experienced mechanics. The manual delves into general information, routine maintenance procedures, engine removal and installation techniques, fuel system intricacies, lubrication and cooling system operations, and engine specifications. It also covers transmission, drive chain and sprocket systems, steering mechanisms, shock absorbers, bodywork components, intake and exhaust systems, and the electrical system. Furthermore, the manual includes advanced troubleshooting guides to help diagnose and resolve complex issues. With its thorough coverage and easy-to-understand format, this repair manual empowers you to confidently tackle any repair or maintenance task on your Yamaha outboard motor.

The 1988-1994 Yamaha 70HP and 90HP 2-stroke outboard motors represent a significant era in Yamaha's marine history, offering dependable power and rugged performance for a wide range of boating applications. These engines, often referred to as the "70/90 series," were renowned for their robust construction, reliable operation, and relatively straightforward maintenance. Featuring a two-cylinder, two-stroke design, these outboards delivered impressive power output for their size, making them popular choices for fishing boats, runabouts, and smaller pontoon boats. The 70HP model provided ample power for leisurely cruising and fishing, while the 90HP version offered more punch for towing water skiers or navigating choppy waters. These Yamaha outboards were known for their simplicity, featuring a carburetor-based fuel system and a manual starting mechanism. The engines were also relatively lightweight, contributing to their maneuverability and ease of installation. Despite being two-stroke engines, they boasted good fuel efficiency for their time due to their compact design and well-engineered combustion chambers. They also employed a reed valve intake system, which contributed to their smooth acceleration and responsive throttle response. While newer, four-stroke outboards have since surpassed them in terms of fuel economy and emissions, the 70/90 series remains a respected choice for boat owners seeking reliable and robust power, particularly within the used market. With proper maintenance and care, these engines can provide years of faithful service.