This manual covers the Volvo Penta AQ131 marine engine, designed for internal combustion applications. While specific production years are not detailed, this workshop service and repair manual provides comprehensive information for owners and technicians. The AQ131 is a 4-cylinder, naturally aspirated engine with an approximate displacement of 2.3 liters, typically producing between 130 and 150 horsepower. It features a closed cooling system with a heat exchanger and is commonly paired with Volvo Penta sterndrive or inboard-outboard transmission systems. The purpose of this extensive English-language manual is to guide users through the maintenance, troubleshooting, and repair of the Volvo Penta AQ131 engine. It includes detailed procedures for periodic maintenance, step-by-step repair instructions, overhaul guidance, and wiring diagrams. Additionally, the manual provides essential technical specifications and safety guidelines necessary for proper operation and upkeep. This resource is invaluable for ensuring the longevity and optimal performance of your marine engine.