Abstract: Described is novel apparatus for rendering a watercraft propulsion system universal. One embodiment of the invention comprises a rotary shaft; a propeller detachably attached to one end of the rotary shaft, the other end of the rotary shaft being configured for detachable and either direct or indirect connection to, and rotational relationship with, a drive shaft of the engine; a plate which is directly or indirectly pivotally attached to a stern portion of the watercraft and which, during normal operation, is disposed in a substantially horizontal plane above the propeller, the plane of the plate traversing the rotary shaft; and a hollow heat-conductive loop integral with or connected to the apparatus and connected to the cooling system for circulating a flow of the fluid from the cooling system through the loop and thence back to the cooling system, the loop being adapted to be disposed in thermally-conductive heat exchange contact with the water when the watercraft is being propelled by the engine.

Abstract: Novel apparatus and methods for cooling a watercraft internal combustion engine which supplies rotational force to a drive unit attached to the watercraft are described. The apparatus comprises a heat exchanger connected to or integral with the drive unit, the heat exchanger having therein a hollow loop connected to the engine cooling system for circulating a flow of fluid from the cooling system through the loop and thence back to the cooling system. The heat exchanger is adapted to be disposed in thermally-conductive heat exchange contact with water when the watercraft is being propelled by the drive unit. In a preferred embodiment, the heat exchanger extends from the watercraft in a substantially horizontal plane which is no lower than the bottom of the watercraft, is disposed above a propeller connected to the drive unit, and is sized and configured to deter cavitation around the propeller.

Abstract: A hollow hub has around its exterior a plurality of apertures for individually receiving a respective cylindrical inner end portion of one of a plurality of axially rotatable propeller blades. Additionally, the hub has around its exterior a plurality of arcuate recesses for (a) individually receiving an inner portion of one of the respective propeller blades when the cylindrical inner end portion of that blade is received in one of the apertures, and (b) accommodating arcuate movement of the blade inner portion upon axial rotation of the cylindrical inner end portion of the blade.

Abstract: Stern drive propulsion systems for boats in which there is at least one prime mover (outboard or inboard motor) and a power train for rotating at least one propeller in the water to propel the boat are improved by inclusion therein of novel variable pitch propellers, and a novel pitch adjusting propulsion system. The system includes a blade and hub mechanism that can propel the boat forwardly and in reverse with great maneuverability, and cut through mud and thick vegetation without becoming fouled, as well operate the boat at high speeds in open water.

Abstract: A propeller blade having (i) a planar configuration (ii) an inner end portion, (iii) an outer end portion, (iv) a relatively sharp, outwardly swept back leading edge portion, and (v) a cylindrical stub axially aligned with the plane of the blade and affixed to the inner end portion of the blade. Also described is a mechanism that enables the pitch of the blades to be adjusted by the operator through a continuum of positions ranging from fast forward to fast reverse so that the boat can be operated at a full range and variety of speeds, can be stopped rapidly, and can be maneuvered with precision. The mechanism can be used for operating flat-bottom boats ("mud boats") in swamps, shallow water, bayous, lakes, rivers and the like, and pass through wet mud and swampy marshes choked with mud or vegetation without excessively fouling the propellers. The mechanism can be serviced and repaired easily and quickly, and can be employed to operate small craft such as mud boats with a minimum loss of interior boat space.