This comprehensive service and repair manual covers Mercury Mercruiser #4 Stern Drive Units, models MCM 120-260, encompassing production years 1978 through 1982. It provides detailed instructions and guidance for complete tear-down and rebuild procedures, ensuring you have the knowledge and resources to tackle any repair or restoration project. Within this manual, you'll find an abundance of illustrations, diagrams, wiring schematics, and specifications, all meticulously designed to guide you through each step. The manual covers a wide range of topics, from routine maintenance and troubleshooting to complex repair procedures, making it an invaluable resource for both novice and seasoned mechanics. Specific content within this manual includes: * **General Information:** A foundational section providing essential background knowledge about the Mercury Mercruiser #4 Stern Drive Units. * **Troubleshooting:** A dedicated section for identifying and resolving common issues, empowering you to diagnose problems efficiently. * **Drive Unit:** In-depth coverage of the Drive Shaft Housing Assembly and Gear Housing Assembly, enabling you to understand and repair these essential components. * **Transom Plate Assembly:** Comprehensive guidance on the structure and repair of the Transom Plate Assembly. * **Power Trim:** Detailed instructions for maintaining and repairing the Power Trim system. * **Power Steering:** Guidance on servicing and troubleshooting the Power Steering system. * **Service Bulletins:** Access to official service bulletins, ensuring you have the latest information and updates. This comprehensive manual is organized for easy navigation and includes clear, concise language, making it a user-friendly resource for all skill levels. Whether you're a seasoned mechanic or a DIY enthusiast, this manual will equip you with the knowledge and expertise to keep your Mercury Mercruiser #4 Stern Drive Units running smoothly.

The Mercury Mercruiser Number 4 Stern Drive Units MCM 120-260, produced from 1978 to 1982, were a pivotal component in the evolution of recreational boating. These stern drive units, specifically designed for Mercury Mercruiser inboard-outboard (IO) systems, were renowned for their robust construction, reliable performance, and user-friendly design. The MCM 120-260 series encompassed a range of power outputs, from the 120-horsepower MCM 120 to the 260-horsepower MCM 260, catering to a diverse spectrum of boat types and boating styles. These units featured a compact and efficient design, integrating the engine, transmission, and drive unit into a single, self-contained package. This integration simplified installation and maintenance, making them highly appealing to boat owners seeking a seamless and dependable power solution. The Mercury Mercruiser Number 4 Stern Drive Units MCM 120-260 were characterized by their innovative features, such as the integrated power steering system, which provided precise and responsive handling. Their robust construction, incorporating high-quality materials and meticulous engineering, ensured durability and longevity even in demanding marine environments. The MCM 120-260 units were also known for their smooth and quiet operation, minimizing noise and vibration levels for a more enjoyable boating experience. The combination of performance, reliability, and user-friendly features made the Mercury Mercruiser Number 4 Stern Drive Units MCM 120-260 a popular choice for boat owners seeking a balanced and efficient power solution. They played a significant role in shaping the recreational boating landscape during the late 1970s and early 1980s, leaving a lasting legacy in the marine industry.