This service repair manual provides comprehensive information for the Mercury Mariner Outboard 30/40 HP 2-stroke engines. These engines are designed for marine applications and are known for their robust construction and reliable performance, offering 30 HP and 40 HP variants suitable for a range of boating needs. The 2-stroke, 2-cylinder configuration ensures efficient power delivery for various watercraft. This manual covers essential maintenance procedures, troubleshooting guides, detailed technical specifications, and critical safety guidelines. It is an indispensable resource for owners, mechanics, and technicians seeking to maintain, repair, and optimize the performance of their Mercury Mariner outboard engines. The content is presented in English and is designed to facilitate a thorough understanding of the engine's systems and operational requirements.