Abstract: A transmission set for planing motorboats, comprising a fixing bracket (16) which at the same time allows to firmly block the containing box linked and engaged to the stern of the hull, in an absolutely invariable position: said bracket (16) is provided with two longitudinal arms placed in such a way as to support in a fixed point a rotating propeller element in such a way as to receive the hooking of the stern part of the motor or of the inverter connected to the motor, in a constant manner placed in height and in distance, but with the possibility of rotating in a radial direction with respect to the centre of above mentioned elastic support of the stern and therefore of giving the possibility of placing in the position considered the most appropriate said elastic supports of the stern of the engine.