This comprehensive service manual covers Mercury marine diesel engines, specifically the D2.8L D-Tronic and D4.2L D-Tronic models. These inline diesel engines are designed for a variety of marine applications, including sterndrive (MCM) and inboard (MIE) configurations. Engineered for reliability and performance, these engines represent a significant advancement in marine propulsion technology, providing efficient and powerful operation for demanding maritime use. This manual serves as an essential resource for owners, mechanics, and technicians. It provides detailed information on general operations, routine maintenance schedules, engine removal and installation procedures, and in-depth troubleshooting guides. Coverage extends to critical systems such as fuel, lubrication, cooling, electrical, and transmission, along with detailed engine specifications. The objective is to empower users with the knowledge necessary to maintain, repair, and optimize the performance of their Mercury marine diesel engines.