This workshop service repair manual covers the Mercury Mariner Marathon, a marine engine designed for reliable performance. This 2-cylinder, 30 cubic inch, 30 HP water-cooled gasoline engine is equipped with an outboard lower unit transmission. While specific production years are not detailed, the engineering and robust construction of the Mercury Mariner series are known for their durability and efficiency in marine applications. This comprehensive English-language manual provides essential information for mechanical technicians. It details scheduled maintenance items such as fuel filter replacement and water pump impeller replacement, alongside critical technical specifications and repair procedures. The manual serves as an indispensable resource for understanding, maintaining, and repairing the Mercury Mariner Marathon, ensuring its optimal operational status and longevity.