Propulsion unit for shallow draft boats or the like

Claim 1

IN A SHALLOW DRAFT BOAT HAVING A SUBSTANTIALLY FLAT BOTTOM WITH AN OPENING THEREIN, AN IMPROVEMENT IN A PROPULSION UNIT THEREFOR COMPRISING: A HOUSING ATTACHED TO THE BOTTOM OF THE BOAT AND CLOSING THE OPENING THEREOF, A SECOND HOUSING MOUNTED WITHIN SAID FIRST HOUSING AND ROTATABLY ADJUSTABLE ON A VERTICAL AXIS WITH RESPECT TO THE FIRST HOUSING, SAID SECOND HOUSING HAVING A PLANAR BOTTOM PORTION LYING SUBSTANTIALLY IN THE PLANE OF THE FLAT BOTTOM OF THE BOAT, SAID SECOND HOUSING HAVING AN INLET OPENING IN ITS PLANAR BOTTOM PORTION COAXIAL WITH THE VERTICAL AXIS OF ROTATION OF THE SAME AND AN OUTLET OPENING IN ITS PLANAR BOTTOM PORTION SPACED RADIALLY OUTWARDLY FROM THE INLET OPENING, SAID INLET OPENING BEING CIRCULAR IN CROSS-SECTION AND SAID OUTLET OPENING BEING ELONGATED AND HAVING A CROSS-SECTIONAL AREA SUBSTANTIALLY EQUAL TO THE CROSS-SECTIONAL AREA OF SAID INLET OPENING, A DUCT IN SAID SECOND HOUSING HAVING A PORTION EXTENDING VERTICALLY UPWARDLY FROM THE INLET OPENING AND THEN ANOTHER PORTION EXTENDING IN A RADIAL PLANE TO THE VERTICAL AXIS OF THE VERTICAL PORTION AND DOWNWARDLY TO THE OUTLET OPENING FOR PROVIDING A CHANNEL FOR WATER HAVING ONE CHANGE OF DIRECTION THEREIN, THE DOWNWARDLY EXTENDING PORTION OF SAID DUCT COMMUNICATING WITH THE OUTLET OPENING AT AN ACUTE ANGLE TO THE PLANE OF THE SAME, SAID DUCT HAVING A CROSS-SECTIONAL AREA THROUGHOUT ITS LENGTH SUBSTANTIALLY EQUAL TO THE CROSS-SECTIONAL AREA OF THE INLET OPENING AND THE OUTLET OPENING, AN AXIAL FLOW PROPELLER SUPPORTED IN THE VERTICAL PORTION OF SAID DUCT AND ROTATABLE ON THE VERTICAL AXIS OF THE SAME FOR DRAWING WATER THROUGH SAID INLET OPENING AND DISCHARGING THE SAME THROUGH SAID OUTLET OPENING, SAID PROPELLER HAVING BLADES WITH LEADING EDGES LYING IN THE SAME PLANE AS THE PLANE OF SAID INLET OPENING AND HAVING A MAXIMUM DIAMETER SLIGHTLY LESS THAN THE DIAMETER OF THE VERTICAL PORTION OF SAID DUCT SO THE TIPS OF THE BLADE LIE IN CLOSE PROXIMITY TO THE WALLS OF THE VERTICAL PORTION OF THE DUCT, AND MEANS FOR ROTATING SAID PROPELLER.