This document pertains to the Mercury Mariner JET outboard motor, specifically models from the 20 HP series, designed for various marine applications. These engines are recognized for their robust construction and reliable performance, incorporating a water-cooled system and a CDI ignition for efficient operation. The jet drive transmission offers a unique propulsion method, suitable for shallow water navigation. This manual covers models with serial numbers 0G044027 (US) and 09807909 (Belgium) and above, ensuring precise coverage for these specific units. This comprehensive Workshop Service Repair Manual provides detailed guidance for the maintenance, repair, and troubleshooting of your Mercury Mariner JET outboard motor. It includes essential information on engine specifications, lubrication, fuel and oil requirements, and safety features such as the standard kill switch with lanyard. Whether you are a seasoned technician or an owner performing routine upkeep, this manual is an indispensable resource for ensuring the longevity and optimal performance of your marine engine.