Water jet propulsion boat and boat

Abstract

A water jet propulsion boat includes a boat body including a keel, and a cavity in a front portion of the keel extending in a left-right direction of the boat body.

What is claimed is: 
     
         1 . A water jet propulsion boat comprising:
 a boat body including a keel; and   a cavity in a front portion of the keel extending in a left-right direction of the boat body.   
     
     
         2 . The water jet propulsion boat according to  claim 1 , wherein at least a portion of the cavity is below a waterline of the water jet propulsion boat when the water jet propulsion boat is travelling. 
     
     
         3 . The water jet propulsion boat according to  claim 2 , wherein a portion of a front side of the cavity is above the waterline when the water jet propulsion boat is travelling. 
     
     
         4 . The water jet propulsion boat according to  claim 1 , wherein the cavity is adjacent to a lower surface of the boat body. 
     
     
         5 . The water jet propulsion boat according to  claim 1 , wherein the boat body includes:
 a boat main body; and   a plate including a front end portion and a rear end portion each connected to a lower portion of the boat main body, and a middle portion between the front end portion and the rear end portion spaced apart from the boat main body in an upper-lower direction of the boat body; wherein   the cavity defines a space between the boat main body and the plate.   
     
     
         6 . The water jet propulsion boat according to  claim 5 , wherein, when viewed in the left-right direction, an upper contour line of the plate includes a curved shape or a shape including a portion bent at an angle of more than about 90 degrees and less than about 180 degrees. 
     
     
         7 . The water jet propulsion boat according to  claim 5 , wherein, when viewed in the left-right direction, a lower contour line of the plate includes a curved shape. 
     
     
         8 . The water jet propulsion boat according to  claim 5 , wherein the plate has a cross-section intersecting the front-rear direction such that a central portion of the plate located adjacent a centerline of the boat body in the left-right direction projects downward. 
     
     
         9 . The water jet propulsion boat according to  claim 8 , wherein the plate has a cross-section intersecting the front-rear direction that is triangular or substantially triangular in shape, and includes a corner located adjacent the centerline of the boat body in the left-right direction and that projects downward. 
     
     
         10 . The water jet propulsion boat according to  claim 5 , wherein, when viewed in the left-right direction, an angle between the rear end portion of the plate and the boat main body is less than an angle between the front end portion of the plate and the boat main body. 
     
     
         11 . The water jet propulsion boat according to  claim 5 , wherein the plate is removably connected to the boat main body. 
     
     
         12 . The water jet propulsion boat according to  claim 1 , wherein, when viewed in an upper-lower direction of the boat body, a rearward contour line of the cavity includes a center portion adjacent to a left-right centerline of the boat body and that projects forward. 
     
     
         13 . The water jet propulsion boat according to  claim 12 , wherein, when viewed in the upper-lower direction, the rearward contour line of the cavity includes a corner adjacent to the left-right centerline of the boat body and that projects forward. 
     
     
         14 . The water jet propulsion boat according to  claim 1 , wherein the cavity extends in a front-rear direction of the boat body. 
     
     
         15 . The water jet propulsion boat according to  claim 1 , wherein the cavity includes a plurality of cavities in the front portion of the keel that are aligned in a front-rear direction of the boat body. 
     
     
         16 . A boat comprising:
 a boat body including a keel; and   a cavity in a front portion of the keel extending in a left-right direction of the boat body.