This manual covers the Mercury Mariner 30 Sea Pro outboard motor, a robust 2-stroke, 2-cylinder engine designed for reliable performance on the water. With a displacement of 423cc and a power output of 30 horsepower (22.1 kW), this carbureted motor features a CDI ignition system and a water-cooled design for efficient operation. Its 20-inch long shaft and 1.83:1 gearcase ratio are optimized for various marine applications, while the electric start and remote steering provide user convenience. The Mariner 30 Sea Pro is engineered for durability and dependable power, making it a strong choice for boaters seeking consistent performance. The purpose of this Service Repair Manual is to provide comprehensive guidance for the maintenance, repair, and servicing of the Mercury Mariner 30 Sea Pro outboard motor. It details essential procedures, including lubrication requirements with Mercury Outboard 2-Cycle Oil at a 50:1 ratio, recommended spark plug specifications (NGK BUHW), and cooling system maintenance. Technical specifications, troubleshooting information, and safety guidelines, such as the emergency kill switch, are also included to ensure the motor operates at peak efficiency and safety. This manual serves as an indispensable resource for owners, technicians, and mechanics to preserve the longevity and performance of their Mercury outboard.