This service repair workshop manual covers Mercury/Mariner 9.9/15 HP outboard engines manufactured between 1998 and 1999. These 4-stroke engines, available in 9.9/15 HP and 9.9/15 Bigfoot configurations, feature a 323 cc displacement and DOHC design. Fuel delivery is managed through multi-point sequential electronic fuel injection (EFI) or carburetors on certain models, while water cooling ensures efficient operation. The engines offer both electric and manual starting systems and utilize a Forward-Neutral-Reverse transmission with standard or counter-rotating propeller shaft options. This comprehensive manual provides essential information for maintaining and repairing your Mercury/Mariner outboard. It details maintenance schedules, including procedures for spark plugs, fuel lines, oil changes, and water pump replacement, along with inspection guidelines for anodes, bonding wires, and timing belts. Technical specifications and troubleshooting guidance are included to assist owners, mechanics, and technicians in ensuring optimal performance and longevity of the engine.