Patent ID: 8800463

Claim:
A boat comprising: a propeller tunnel portion formed in a hull of the boat; an output shaft extending from said propeller tunnel portion; a propeller comprising a plurality of blades, said propeller rotating on said output shaft, said propeller defining an outer diameter, a forward plane perpendicular to said output shaft and defined by a forward-most extension of said blades of said propeller, and an aft plane perpendicular to said output shaft and defined by an aft-most extension of said blades of said propeller; a protrusion having a curved portion that terminates in a tip portion and provides a cowl around at least a portion of said propeller, said protrusion inwardly extends a distance from a surface of said propeller tunnel portion and said tip portion terminates at or abaft said aft plane, and wherein said cowl has an edge disposed at or abaft said aft plane of said propeller, further wherein said propeller tunnel portion defines a contoured portion configured to serve as an inflow opening ahead of said forward plane, wherein said contoured portion defines a maximum radius (R I ) according to the formula, R I = R P slip where (R P ) is a radius dimension of said propeller, and (slip) is a ratio of the propeller speed of advance divided by the product of a shaft rotational velocity and a pitch of said propeller.