This manual covers the Yamaha F100B / F100C Outboard, a four-stroke engine designed for reliable performance. With a 100 HP output, this engine features a 4-cylinder configuration, a displacement of 1596 cc (97.4 ci), and specific bore and stroke dimensions of 81 mm (3.19 in) and 78.4 mm (3.09 in) respectively. It is equipped with an outboard gearcase offering Forward-Neutral-Reverse shifting and a forward gear ratio of 2.00:1. Available shaft lengths include 20 inch (L) and 25 inch (X), making it a versatile option for various marine applications. This comprehensive Service Repair Workshop Manual in English provides essential information for maintaining and repairing your Yamaha outboard. It details general information, specifications, periodic checks and adjustments, fuel system, power unit, lower unit, bracket unit, and electrical systems. Furthermore, it includes a troubleshooting guide and an index to assist owners, mechanics, and technicians. The manual outlines maintenance procedures such as initial oil changes at 10 operating hours and subsequent changes every 100 operating hours or annually, specifying the use of Yamaha Gear Oil or equivalent API GL-4 for its approximately 800 ml (27 fl. oz.) gear oil capacity.