Chain drive marine propulsion system with dual counterrotating propellers

In a marine drive for a boat, said marine drive including an engine having a rotatable crankshaft and a depending gearcase, the improvement comprising:

• first and second concentric propeller shafts mounted to said depending gearcase, each said propeller shaft having a portion projecting from said gearcase;
• a first propeller mounted to said projecting portion of said first propeller shaft;
• a second propeller mounted to said projecting portion of said second propeller shaft;
• one or more intermediate shafts disposed between said engine crankshaft and said first and second propeller shafts, said one or more intermediate shafts carrying first and second sprockets;
• chain means drivingly interconnected between said first and second sprockets and said first and second propeller shafts, said chain means including a first portion for driving said first propeller shaft and a second portion for driving said second propeller shaft;
• and
• counterrotation drive means for driving said first and second portions of said chain means in opposite directions, and thereby providing rotation of said first and second propeller shafts in opposite rotational directions, wherein said counterrotation drive means causes said first and second sprockets on said one or more intermediate shafts to be driven in opposite rotational directions, thereby resulting in driving of said first and second portions of said chain means in opposite directions.