This workshop service repair manual covers the Mercury Mariner DFI Optimax outboard engine. Engineered for reliability and performance, this water-cooled, direct fuel injection engine family is known for its advanced technology, including Electronic Throttle Control (ETC) and Onboard Diagnostics (OBD-III). The engine delivers 200 horsepower and utilizes a CDI ignition system, making it a robust choice for various marine applications. This manual is presented in English and is designed to provide comprehensive technical information for maintaining and servicing this specific engine variant. The purpose of this manual is to serve as a definitive guide for owners, mechanics, and technicians. It details essential maintenance procedures, including lubrication requirements, scheduled service intervals for components like spark plugs and fuel filters, and water pump impeller replacement. Furthermore, it provides in-depth troubleshooting guidance, technical specifications, and safety protocols necessary for the proper upkeep and repair of the Mercury Mariner DFI Optimax engine. Adhering to the procedures outlined within will ensure optimal performance and longevity of the marine propulsion system.