This service repair manual covers Mercury Mariner outboard engines, including the 20 JET, 20, 25, 25 MARATHON, and 25 SEAPRO models. These engines are designed for marine applications and offer reliable performance. The manual provides comprehensive information to assist with the upkeep and restoration of these outboard units, ensuring their continued operational efficiency. This manual is an essential resource for owners and professional technicians alike, detailing repair, service, restoration, maintenance, rebuilding, and diagnostic procedures. It includes clear, step-by-step instructions with illustrations, component breakdowns, and exploded views. Key areas covered include general information, installation, electrical systems, fuel systems, powerhead, mid-section, lower unit, gear housing, and specific drive systems like the jet drive. Troubleshooting support is also provided to address potential issues.