This manual covers Mercury/Mariner Optimax DFI outboard engines. These engines are known for their Direct Fuel Injection (DFI) technology, offering robust performance and efficiency across various horsepower options, including 200 Hp, 225 Hp, and 250 Hp variants. The Optimax DFI generation represents a significant advancement in marine propulsion, engineered for reliability and optimal operation in demanding aquatic environments. This comprehensive service manual is designed to assist owners and experienced mechanics in understanding and maintaining these powerful marine engines. The purpose of this complete service manual is to provide detailed guidance for the maintenance, repair, and troubleshooting of Mercury/Mariner Optimax DFI engines. It includes step-by-step instructions, accompanied by hundreds of photos and illustrations, covering all aspects of engine service. Key areas addressed include lubrication, fuel and ignition systems, powerhead and gearcase service, tilt and trim, oil injection, and electrical systems with detailed wiring diagrams. The manual also features comprehensive diagnostic procedures and electrical troubleshooting guidance, ensuring that both do-it-yourself enthusiasts and professional mechanics have the resources needed to keep these engines running at peak performance.