This manual covers Mercury Mercruiser #6 Sterndrive Units, specifically the R, MR, Alpha One, and Alpha One SS models manufactured between 1983 and 1990. These first-generation sterndrives are known for their robust engineering and reliability, designed to be paired with a variety of petrol engines. The units are equipped with advanced features for their time, including power and manual steering systems, and comprehensive corrosion protection. This documentation is essential for understanding and maintaining these high-performance marine propulsion systems. The Mercury Mercruiser #6 Sterndrive Units R, MR, Alpha One, Alpha One SS 1983-1990 Service Repair Manual provides detailed guidance for owners, mechanics, and technicians. It encompasses a wide range of essential information, including preventative maintenance, detailed servicing procedures, repair instructions, and rebuilding processes. The manual also offers troubleshooting support for immediate problem resolution and includes critical technical specifications such as serial number ranges for different models, power trim systems, and gear ratios. This comprehensive resource ensures the longevity and optimal performance of your sterndrive unit.