This Service Repair Manual covers the Volvo Penta 251DOHC engine, a DOHC Inline 4-cylinder model with a 2.5-liter displacement. While specific production years are not detailed, this engine is designed for marine applications and features fuel injection and a water-cooled system. Its engineering is built upon Volvo Penta's reputation for reliability and performance in demanding environments, making it a robust choice for various boating needs. This manual provides comprehensive guidance for maintaining and repairing the Volvo Penta 251DOHC engine. It details in-depth service procedures, technical specifications, and essential maintenance schedules, including information on oil changes, filter replacements, and spark plug specifications. This professional-quality English language resource is designed to assist owners, technicians, and mechanics in ensuring the optimal performance and longevity of their engine.