This manual covers the Mercury MerCruiser D2.8L, D4.2L, and D-Tronic marine diesel engines, designed for a wide range of marine applications. These in-line diesel engines are engineered for reliable performance and efficient operation using diesel fuel. Their robust construction and advanced D-Tronic systems ensure dependable power for various watercraft, from personal recreational vessels to larger commercial applications. The purpose of this comprehensive repair and workshop manual is to provide detailed guidance for maintaining and repairing your Mercury MerCruiser marine diesel engine. It covers essential areas including general information, routine maintenance, engine removal and installation, fuel and lubrication systems, cooling systems, transmission, steering, electrical systems, and advanced troubleshooting. This resource is invaluable for owners, mechanics, and technicians seeking to ensure the optimal performance and longevity of their marine diesel engines.