This service and repair manual covers the Yamaha F100X and F80X outboard motors manufactured in 1999. These four-stroke, gasoline-powered marine propulsion units are engineered for reliable performance on the water. The manual details specific models including F100TLRX, F100TXRX, F80TLRX, and F80TXRX, offering insights into their robust construction and operational capabilities. This comprehensive English-language manual provides essential information for maintaining and repairing your Yamaha outboard motor. It includes detailed procedures for periodic inspection and adjustment, as well as troubleshooting guidance for various systems such as the fuel, power, lower, bracket, and electrical units. With good quality pictures, this manual serves as a vital resource for owners and technicians alike to ensure the longevity and optimal performance of the motor.