Abstract: A dual counterrotating propeller drive mechanism for a marine propulsion system incorporates a torque splitting device which consists of a differential gear means and a ratio gear means. The torque splitting device assigns a selectable fixed fraction of the engine torque to each propeller regardless of power, thrust, and speed conditions. The rear one of the two propellers adjusts its rotational speed relative to the front propeller in response to changes in the front propeller's wake and in this way maintains optimum propulsive efficiency over a wide range of operating conditions. Furthermore, precise matching of front and rear propeller parameters for a given application is no longer required.

Abstract: A marine stern drive unit is mounted aft of the boat transom on a rigid lift arm in a manner allowing the drive unit to be independently trimmed or moved vertically up or down. The drive unit is pivotally attached to the aft end of the lift arm for trimming movement about a generally horizontal axis and the lift arm is pivotally attached to the boat to rotate about a second horizontal axis such that the drive unit is moved generally vertically. The boat engine is preferably mounted transversely and power transmission from the engine to the drive unit is provided by a flexible drive belt which is supported by the rigid lift arm. Separate trim and lift movement is supplied to the drive unit by individual fluid cylinders. The trim cylinder operatively interconnects the drive unit with the boat hull or the forward end of the lift arm. The lift cylinder operatively interconnects the boat hull and the lift arm at a point aft of its pivotal connection to the boat.

Abstract: A system for optimizing the operating efficiency of a boat by balancing fuel consumption against cruising speed utilizes a comparison between engine speed and boat speed to effect automatic positioning of the drive unit. The measurements of boat and engine speed before and after an incremental change in vertical position or trim position are used to calculate the percent changes in boat speed and engine speed which, in turn, are used in conjunction with selected minimum and maximum incremental percentages to effect subsequent alternate control strategies. Depending upon the relative difference in the percent changes in boat and engine speeds, including adjustments based on the minimum and maximum incremental percents, the system will automatically continue incremental movement of the drive unit in the same direction, hold the drive unit in its present position, or move the drive unit an incremental amount in the opposite direction.

Abstract: A system for optimizing the operation of a marine drive of the type whose position may be varied with respect to the boat by the operation of separate lift and trim/tilt means includes an automatic control system which stores preselected drive unit positions for various operating modes and is operative to return the drive unit to any pre-established position by pressing a selected operating mode positioning button. The various operating modes may include cruising, acceleration, trolling and trailering position, any of which may be selectively modified to accomodate changes in both operating or environmental conditions. This system may incorporate other optimization routines and/or automatic engine protection systems to provide virtually complete push button operation for complex marine drive unit positioning mechanisms.

Abstract: A transom extension assembly, particularly useful for smaller or auxiliary outboard motors, utilizes a pivotally connected 4-leg linkage and an operatively connected fluid power operator to lift the motor vertically with respect to the boat transom. The fluid power lift includes a mechanical latching apparatus by which the motor may be releasably held in its raised position and supported in its lowered position in a manner to relieve the hydraulic system from all other operating loads. The apparatus may include its own fluid pressure supply or may utilize fluid pressure from another boat system.

Abstract: An outboard motor tilt mechanism includes a tilt position bracket pivotally attached to the motor swivel bracket and operatively attached to the fixed motor transom bracket such that upward rotation of the swivel bracket provides step-wise engagement between tilt position notches in the tilt position bracket and abutment means on the transom bracket. A control bracket mounted for limited rotation with and frictional engagement of the tilt position bracket operates to prevent reengagement of a tilt position notch once the swivel bracket has been rotated upwardly past the point of initial engagement such that return downward rotation to the lower operating position is effected automatically. The mechanism may be configured to provide automatic latching in the uppermost trailering position with either manually effected or automatic return therefrom to the lower operating position.

Abstract: A snowmobile drive track assembly includes an endless belt unit having a central drive belt section and laterally spaced belt sections interconnected by flat, spring-steel track bars. The several sections include longitudinally aligned ground-engaging drive ribs holding the bars in spaced relation to the ground. The bars are molded into the outer surface of the ground engaging side of the belt immediately adjacent the wall of the depending snow engaging ribs. The bar extends essentially completely throughout the width of the three sections with the undersurface completely exposed and drive lugs provided on the backside of the central section. The exposure of the bars on the outer side of the track unit essentially throughout the complete width of the track unit significantly increases the heat dissipating characteristics of the belt unit. The belt is suitably reinforced by embedding of nylon fabric and longitudinal cords.