This International Standard specifies the requirements for the design, materials, construction, installation and testing of permanently installed fuel systems as installed for internal combustion engines. It applies to all parts of permanently installed diesel and petrol fuel systems as installed, from the fuel fill opening to the point of connection with the propulsion or auxiliary engine on inboard- and outboard-powered small craft of up to 24 m hull length. Requirements for the design, materials, construction and testing of permanently installed fixed fuel tanks are given in ISO 21487.