This service repair manual provides comprehensive information for Yamaha 25J, 30D, 25X, and 30X outboard motors. These 25 HP and 30 HP outboard engines are engineered for reliable performance in various marine applications. This manual covers a wide range of models, including specific variants like the 25JMH, 30DMH, and 30DEHO, with detailed serial number ranges to ensure accurate identification and service. The robust design and engineering of these Yamaha outboard motors ensure durability and efficiency for recreational and professional use. The purpose of this manual is to guide owners, mechanics, and technicians through the maintenance, repair, and troubleshooting of these Yamaha outboard motors. It includes detailed sections on general information, specifications, periodic inspections and adjustments, fuel systems, power units, lower units, bracket units, electrical systems, and comprehensive trouble-analysis guides. By following the procedures outlined, users can effectively maintain their engines, ensure optimal performance, and extend the lifespan of their Yamaha outboard motors.