This service repair manual covers Mercury Mariner outboard motors, specifically the 225 EFI, 250 EFI, 3.0 Litre Marathon, and 3.0 Litre SeaPro models. These powerful V6 engines, featuring 3.0 Litre displacement and Electronic Fuel Injection (EFI), are engineered for reliable performance in demanding marine environments. The manual is designed to provide comprehensive information for maintaining and repairing these robust outboard motors, ensuring their continued operational efficiency. This manual serves as an essential resource for DIY enthusiasts, professional technicians, mechanics, and workshops. It details critical maintenance procedures, troubleshooting guidance, technical specifications, and safety protocols. With clear, step-by-step illustrations, zoomable images, and exploded component diagrams, this English-language manual facilitates efficient and accurate work, enabling users to effectively service and repair their Mercury Mariner outboard engines.