Abstract: A horizontally elongated panel constructed of dielectric material is provided including front and rear ends. The panel is provided with a longitudinal slot closed at its forward end and open at its rear end and the front end of the panel is forwardly and upwardly curved. The lower unit of an outboard motor is forwardly, snugly seatable within the slot and the panel is mountable from the opposite side outwardly projecting cavitation plate portions of the lower unit. The panel functions as a water confining panel for disposition substantially at the surface of an associated body of water for sealing the area in which the outboard motor propeller turns against the entrance of ambient air into the water from above the water surface.