Engine for driving a watercraft propelled by a water jet

#1. Field of the Invention

#This invention relates generally to a watercraft propelled by a water jet, and in particular, to an internal combustion engine for driving the propulsion system of such a watercraft.

#2. Description of the Prior Art

#The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which:

#FIG. 1 is a cross-sectional side view of an engine-powered kayak showing the water induction system and engine;

#FIG. 2 is partial cross section side view of the engine and water induction system shown in FIG. 1;

#Referring now to FIG. 1, a kayak 10 includes a sealed hull portion 12 covered with a seamless molded plastic skin, the hull being formed with a recess 14 on its upper surface 15, in which recess the rider sits facing forward with legs straddling a manually-operated control lever 16 (called a joystick) and feet supported on foot rests. The volume of hull 12 between its upper deck 15 and its bottom surface 17 is filled with a core material 20 that reinforces, strengthens and stiffens the hull. The core 20 may be expandable, cellular molded foam or a hollow, hexangular honeycomb whose walls are of Kevlar or a similar synthetic material. Alternatively, the core may be machined foam. The hull portion 12 is sealed, thereby preventing entry of water from waves or spray and making it possible to roll the kayak upright again following a tip over without it filling with water.

#A seat back 22, secured to the upper surface of the hull 12 supports the seated rider. The core-reinforced portion of the hull 12 is closed by a partition or bulkhead 24, located at the forward end of an engine compartment 26, which contains an engine 28, water intake duct 30, bladed impeller 32 that forces water from the intake duct, and a nozzle 34, whose angular position about a vertical axis can be varied leftward and rightward to steer the kayak 10. Water inducted through duct 30 flows through the impeller and exits through the nozzle 34. The engine compartment 26 is covered with a cowling 36 formed with an air inlet passageway 38. Cowling 36 is secured by latches to the upper surface of the hull, thereby sealing the engine compartment against entry of water when the cowling is latched to the hull. Preferably, engine 28 has a single cylinder and piston, low displacement and operates at high efficiency on a four stroke cycle.

#The intake duct 30, which may be a component separate from the hull 12 or formed integrally with the hull, is of molded plastic having an intake opening 44 in the bottom of the hull, through which water is inducted and flows toward the outlet of nozzle 34. A driveshaft 46, secured to the crankshaft of engine 28 drives the bladed impeller 32 in rotation, thereby drawing water into the intake duct 30 and forcing it through the impeller and out the nozzle 34. A water jet, which propels and steers the kayak 10, rises from the outlet of nozzle 34 into the air above the water surface.