This Service Manual Workshop Guide covers Mercury Mercruiser In-line Diesel engines, specifically the D2.8L D-Tronic and D4.2L D-Tronic variants, designed for Sterndrive (MCM) and Inboard (MIE) applications. These engines feature robust in-line diesel engineering with D-Tronic electronic diesel injection, intercooled turbocharging, and advanced cooling systems. Built for reliability and performance, they are engineered to meet the demands of marine propulsion, ensuring consistent power and efficiency across a range of operational conditions. This comprehensive manual provides essential information for the maintenance, repair, and diagnosis of your Mercury Mercruiser In-line Diesel engine. It details complete step-by-step procedures for preventative maintenance, service, and restoration, along with troubleshooting guidance for immediate problem fixing. Designed for professional technicians, mechanics, workshops, and DIY enthusiasts, this guide offers the technical specifications and expert knowledge necessary to keep your engine operating at peak performance and longevity.