This service repair manual pertains to the Mercury Mercruiser ECM 555. While specific production years are not detailed, this manual covers a critical component known for its role in engine management. The ECM 555 is engineered for reliability and performance within its intended marine applications, ensuring optimal operation of the vessel. This comprehensive manual provides detailed information essential for the maintenance and repair of the Mercury Mercruiser ECM 555. It includes in-depth coverage of diagnostics, service, repair, assembly, and disassembly procedures. Additionally, wiring diagrams for both 10-pin and 14-pin harness configurations are included, along with troubleshooting guidance. This resource is designed to assist owners, mechanics, and technicians in effectively maintaining and repairing the ECM 555.