This service repair manual covers Kohler Marine Generator Sets and Yanmar 4JHL Series Engines. These diesel engines, featuring a 4-cylinder configuration and water cooling, are engineered for reliability in demanding marine environments. While specific production years are not detailed, the manual addresses models that may include naturally aspirated or turbocharged intake systems and wet exhaust configurations, emphasizing their robust construction and efficient operation. The purpose of this manual is to provide comprehensive guidance for the maintenance, repair, and troubleshooting of these engine systems. It details procedures for general inspection, servicing of core engine components, fuel injection equipment, intake and exhaust systems, lubrication, cooling water, and electrical systems. With system-based diagnostics and troubleshooting guides, this manual is an essential resource for owners, mechanics, and technicians to ensure the optimal performance and longevity of their Kohler and Yanmar marine power units.