Patent ID: 8393923

Claim:
A marine propulsion assembly comprising; a marine engine, a pair of parallel laterally spaced propeller shafts and a pair of marine propellers with one of said propellers fixed to each of said shafts for rotation in opposite directions by said marine engine each of said propellers includes a hollow hub and four equally spaced blades and wherein said hub having a forward or first portion having the shape of a frustum of a cone with a decreasing radius from a forward edge thereof to a middle of said hub and a rear or second continuous portion having a shape of a frustum of a cone with an increasing radius from the middle of said hub to the rear of said hub and wherein the base or largest diameter of the frustum of the cones are of equal size; and wherein each of said equally spaced blades having a complex concave shape wherein an arcuate leading edge curves outwardly and upwardly at a reduced radius from a shallow forward portion of said hub to an outwardly extending rear portion with a relatively straight trailing edge that is generally perpendicular to the axis of rotation and wherein the leading edge of one of said propellers face the leading edge of the other of said propellers but spaced apart therefrom by ½ or less of the height of the trailing edge of said blade.