This service repair manual covers Mercury Mariner outboard engines, specifically models including the 225hp, 225 EFI, 250 EFI, 3.0 Litre Marathon, and 3.0 Litre SeaPro, for serial numbers 0D280813 and above. These water-cooled, 3.0 Litre engines offer robust performance with EFI options delivering up to 250hp. Engineered for reliability, these outboards are designed for a wide range of marine applications, providing dependable power and efficiency. This comprehensive manual provides detailed information essential for maintaining and repairing your Mercury Mariner outboard. It includes in-depth coverage of routine maintenance procedures, troubleshooting guidance, technical specifications, and electrical systems, fuel systems, powerhead, mid-section, and lower unit components. With step-by-step instructions and clear illustrations, this manual empowers owners and technicians to perform necessary service, ensuring optimal performance and longevity of the engine.