This Service & Repair Manual covers the Volvo Penta 251DOHC engine, an inline 4-cylinder, naturally aspirated unit featuring DOHC valvetrain and multi-point fuel injection. With a displacement of 2.5 liters (2493 cc), this engine typically produces between 110-120 horsepower and 200-220 Nm of torque, depending on its specific application, which can include marine sterndrive, inboard, or automotive configurations. Its robust engineering ensures reliability and performance, making it a capable choice for various operational needs. This comprehensive manual provides essential information for the maintenance and repair of your Volvo Penta 251DOHC engine. It details critical procedures, technical specifications, and troubleshooting guidance necessary for optimal performance and longevity. Coverage includes lubrication, fluid capacities, recommended service intervals for oil changes, spark plug replacement, and timing belt maintenance, alongside information on its liquid-cooled system and electronic ignition. This resource is designed to assist owners, mechanics, and technicians in effectively servicing and maintaining the engine across all applicable model years.