This service manual covers the Mercury Mariner 200 HP DFI Optimax outboard engine. Engineered for reliable performance, this direct fuel injection (DFI) outboard unit delivers 200 horsepower, featuring advanced electronic ignition and a through-prop exhaust system for efficient operation. Its water-cooled design and safety features, including an emergency kill switch and operator presence control, underscore its commitment to both power and user protection. This manual is intended for a wide range of users, from boat owners to professional technicians, seeking to understand and maintain this robust marine propulsion system. The purpose of this comprehensive service manual is to provide detailed guidance for the maintenance, repair, and technical understanding of the Mercury Mariner 200 HP DFI Optimax outboard. It encompasses essential information on scheduled service procedures, including specific oil and filter requirements, as well as diagnostic and troubleshooting protocols. Technical specifications, operational details, and safety guidelines are thoroughly explained to ensure the longevity and optimal performance of your Mercury Mariner engine. This resource is designed to empower owners and technicians with the knowledge necessary for effective upkeep and repair.