This workshop service manual covers the Mercury Mariner 225 HP DFI Optimax outboard engine, a powerful V6 marine engine renowned for its direct fuel injection technology and robust performance. Designed for a wide range of boating applications, this engine delivers exceptional power and efficiency. Its engineering prioritizes reliability and longevity, making it a trusted choice for demanding marine environments. The DFI Optimax system ensures optimal fuel combustion, contributing to its strong performance characteristics. This comprehensive manual provides detailed instructions for the repair and overhaul of your Mercury Mariner DFI Optimax outboard. It includes essential information on maintenance procedures, troubleshooting common issues, and technical specifications necessary for proper servicing. By following the guidelines within this manual, owners, mechanics, and technicians can effectively maintain and repair the engine, ensuring its continued optimal performance and extending its operational life.