engine in the hull a circulating fuel supply apparatus will now be described a basic structure of the apparatus is similar to that of the above described related art shown in fig6 as shown in fig2 an inlet port 14 a of each injector 14 is connected to the fuel tank 6 via a fuel supply pipe 17 and a fuel pump 18 and an excess fuel return port 14 b of the injector 14 is connected to the fuel tank 6 via a return pipe 19 namely the fuel is sucked from the fuel tank 6 by the fuel pump 18 then pressurized and supplied to each injector 14 via the fuel supply pipe 17 by the fuel pump 18 excess fuel in the injectors 14 is returned to the fuel tank 6 via the return pipe 19 although fig2 shows three injectors 14 in a left portion thereof in addition to the three injectors 14 drawn on the upper side of the engine 11 they are one and the same three injectors 14 the injectors 14 shown in the left portion of the drawing are drawn between the fuel supply pipe 17 and return pipe 19 for the purpose of more clearly showing the fuel circulating path the above described circulating fuel supply apparatus has a heat exchanger 21 for cooling the fuel the heat exchanger 21 is provided in the portion of the fuel supply pipe 17 which is between the fuel pump 18 and the injectors.