The Mercury Marine Mariner Optimax DFI series, produced between 2000 and 2005, represents a significant advancement in outboard engine technology. These 2-stroke direct fuel injection (DFI) engines, available in horsepower ratings from 115 to 175 HP, are engineered for robust performance and reliability across various marine applications. Featuring a 4-cylinder configuration and water-cooled systems, they offer efficient power delivery, supported by electronic ignition and power trim and tilt for optimal operation. Their design emphasizes durability and consistent performance, making them a trusted choice for boaters seeking dependable propulsion. This Service Repair Workshop Manual (WSM) provides comprehensive guidance for the maintenance and repair of the Mercury Marine Mariner Optimax DFI engines. It covers essential procedures, technical specifications, and troubleshooting information necessary for owners, mechanics, and technicians. Within these pages, you will find detailed instructions on lubrication, fuel systems, electrical components, and transmission systems, along with specifications for engine displacement, gear ratios, and charging output. Adhering to the information within this manual will ensure the longevity and optimal performance of your Mariner Optimax DFI engine.