Abstract: A safety shroud for attachment to the rear surface of the transom of an unmodified boat hull equipped with an inboard engine and a propeller tube and shaft rigidly fixed to the engine and extending with clearance through an enlarged opening in the transom, and a propeller on the shaft; the shroud being longitudinally and transversely downward concave to overlie the top and partly enclose the sides of the propeller, the shroud in longitudinal section being upwardly and rearwardly curved from the forward bottom edge of the shroud to just ahead of the propeller zone and then extending straight rearwardly. The lateral edges of the shroud extend generally upwardly and rearwardly from the forward bottom edge of the shroud to merge with the top rear edge thereof. Preferably the shroud is composed of inner and outer interconnected plastic shells, the outer shell having a downward concave reinforcing strut, closed at its bottom by the inner shell, and having a metal rudder support shaft therein.