This manual covers the Mercury Mark I (644cc) marine engine, an internal combustion engine designed for marine applications. Known for its robust engineering and reliability, the Mark I offers dependable performance for various maritime needs. This comprehensive guide is intended to support owners and operators in understanding and maintaining their vessel's propulsion system, ensuring optimal function and longevity. The scope of this Factory Service Repair Manual in English is extensive, detailing everything from routine oil changes to more complex transmission swaps. It provides step-by-step instructions, accompanied by helpful illustrations, to guide users through maintenance procedures and repair tasks. With search and print functionality, this manual is an indispensable resource for owners, mechanics, and technicians seeking to effectively maintain and repair their Mercury Mark I marine engine.