Boat propulsion with surface-running propeller drive

A boat having a transversely convex deep-vee planing type hull in which the bottom of the hull comprises generally flat surfaces which intersect to define the keel of the hull and which extend upward and outwardly from the keel at equal angles between 15.degree. and 30.degree. from the transverse plane through the keel,

• said hull having a transom at the stern extending upwardly and preferably slightly rearwardly from the keel,
• said boat having inboard engine means located aft of the longitudinal center of the boat, the weight and location of the engine means with respect to the hull characteristics being such that at rest in the water, the keel of said hull is inclined forwardly and upwardly at a small angle from the horizontal and at planing speeds the forward and upward inclination of the keel is at a substantially greater angle,
• said hull having a water flow duct in its bottom located to extend forwardly and downwardly from the intersection between the bottom of the hull and the transom, said duct being open downwardly through the bottom of the hull and open rearwardly through the transom,
• a propeller located in alignment with the duct and adjacent the plane occupied by the transom,
• said duct comprising a downwardly and rearwardly open transversely curved channel intersecting the transom to define therewith an opening having an approximate radius slightly greater than the radius of the propeller, and including a top wall which is forwardly and downwardly curved to intersect the bottom of the hull in sharp cornered intersections a short distance forward of the transom, the sharp cornered intersections between the top front wall of said duct and the bottom of said hull being effective at planing speed to cause water flowing rearwardly along the bottom of the hull to break away from the bottom surface of the hull and to prevent this water from flowing along the duct surface into said duct,
• said propeller having a propeller shaft connected to the engine means extending into the interior of the hull and inclined slightly forwardly and upwardly to position the center of rotation of the propeller generally directly astern of and closely adjacent to the horizontal plane which extends rearwardly from the sharp cornered intersections when said boat is at planing inclination to provide for running of said propeller in half-submerged condition,
• a splash guard extending rearwardly of said transom from said duct in general alignment therewith and positioned to intercept the spray produced by said surface running propeller and
• a rudder directly astern of said propeller to receive water projected rearwardly thereby.