This manual covers the Volvo Penta 230, 250, and 251 DOHC marine engines. These engines are engineered for reliable performance in marine applications, reflecting Volvo Penta's commitment to quality and durability. Designed for a variety of maritime uses, these DOHC engines offer robust power and efficiency, making them a trusted choice for boat owners and operators seeking dependable propulsion systems. The purpose of this English-language service and repair manual is to provide comprehensive guidance for all servicing and repairs. It includes routine maintenance procedures, detailed step-by-step instructions, and clear visual aids such as pictures and wiring diagrams. This manual is designed to be easily accessible on PCs, tablets, and smartphones, empowering owners, mechanics, and technicians to effectively maintain and repair their Volvo Penta engines, potentially leading to significant cost savings.