This service repair manual covers Mercury Mercruiser PCM 555 Diagnostics for engines with serial numbers 0M000000 and up. The manual focuses on V8 engines, including the 496 cubic inch (8.1 Liter) displacement variants, and is designed for both High Output (HO) and standard configurations. It provides detailed information to ensure the optimal performance and longevity of these powerful marine engines. This comprehensive English-language manual offers in-depth troubleshooting guidance, assembly and disassembly procedures, and detailed wiring diagrams for various systems, including Mechanical, Integrated, 14 Pin, DTS 5.0, 5.7, and 6.2. It serves as an essential resource for owners, mechanics, and technicians, providing the necessary technical specifications and repair information to maintain and service the PCM 555 Diagnostics system effectively.