This manual covers the Mercury MerCruiser D2.8L and D4.2L D-TRONIC marine diesel engines. These in-line, turbocharged, and intercooled engines are engineered for reliable performance in marine applications. The D-TRONIC fuel system, a common rail injection technology, ensures efficient operation. This manual is designed for use across multiple model years of these engine series, providing essential information for their upkeep and operation. The purpose of this comprehensive repair manual is to provide detailed guidance for the maintenance, troubleshooting, and repair of your Mercury MerCruiser engines. It covers critical systems including fuel, lubrication, intake and exhaust, electrical, and steering. Owners, mechanics, and technicians will find step-by-step procedures, technical specifications, and advanced troubleshooting advice to ensure the longevity and optimal performance of the D2.8L and D4.2L D-TRONIC marine diesel engines.