Abstract: A cooling system of self-propelled floating crane engines, in which an external hydraulic circuit intended to cool internal hydraulic circuits of engines comprises pipelines, pumps, tanks filled with liquid, and skin heat exchangers. The tanks are compulsorily connected to each other and arranged so that a portion of their surface is integrated into an underwater outer skin of a floating crane pontoon, whereas the skin heat exchangers disposed in said tanks are essentially a surface heat exchangers being connected to the internal hydraulic circuit of at least one of the engines, and the pipelines of the external hydraulic circuit are connected to the tanks and to the internal hydraulic circuits of the rest of the engines.