This manual covers the Volvo Penta AQ131 marine engine, a robust inline-4 cylinder unit with a displacement of 2.3 liters and an approximate power output of 130 horsepower. Designed for marine applications, this engine utilizes either a closed cooling system with a heat exchanger or raw water cooling and features a carbureted fuel system. Its engineering prioritizes reliability and performance, making it a dependable choice for various watercraft. This comprehensive full service repair manual is designed for professional technicians and DIY mechanics. It provides detailed information on repair, maintenance, rebuild, refurbish, restore, and diagnostics, including wiring diagrams and troubleshooting procedures. The manual features numbered instructions, sub-steps, notes, cautions, and warnings, alongside detailed illustrations, drawings, and photos to guide users through every task. A numbered table of contents ensures quick access to information, facilitating efficient maintenance and repair of the Volvo Penta AQ131 engine.