Watercraft with sterndrive and hull with vented tunnel

Abstract

A watercraft includes a sterndrive comprising an inboard engine and an outdrive that extends through the transom. The aft end of the hull includes a stepped tunnel, which allows the sterndrive propellers (or other drives) to be operated at a relatively higher position in the water, without unduly decreasing the propeller performance. The stepped tunnel is vented to atmospheric pressure.

1 . A watercraft comprising:
 a hull having a transom, wherein the hull defines a downwardly open stepped tunnel on an aft end of the hull, the stepped tunnel having a forward end defining a step and an open aft end;   an inboard engine;   an outdrive assembly extending from the inboard engine, through the transom, and drivably connected to a propeller or jet pump to provide motive power to the watercraft; and   a vent that provides a flow path from the stepped tunnel to an atmospheric vent port,   wherein the propeller or jet pump is disposed directly aft of the stepped tunnel.   
     
     
         2 . The watercraft of  claim 1 , wherein the outdrive assembly comprises (i) a first drive shaft drivably connected to the inboard engine and extending through the transom, (ii) an upper gearbox disposed outboard of the transom that engages the first drive shaft, (iii) a second drive shaft that engages the upper gear box and extends downwardly, and (iv) a lower gear box that engages the second drive shaft, wherein the propeller or jet pump are drivably connected to the lower gear box. 
     
     
         3 . The watercraft of  claim 1 , wherein the stepped tunnel has a maximum width that is between 25% and 60% of the hull beam. 
     
     
         4 . The watercraft of  claim 1 , wherein the stepped tunnel has a length between 10% and 25% of the hull length overall. 
     
     
         5 . The watercraft of  claim 1 , wherein the vent comprises a plurality of channels, each channel having a first port near the step and an atmospheric port. 
     
     
         6 . The watercraft of  claim 1 , wherein the outdrive assembly is configured such that during operation the propeller or jet pump is positioned to draw water from the stepped tunnel. 
     
     
         7 . The watercraft of  claim 1 , wherein the outdrive assembly is pivotable to move the propeller or jet pump between a lower position wherein the propeller or jet pump is disposed directly aft of the stepped tunnel, and an upper position wherein the propeller or jet pump is disposed away from the stepped tunnel. 
     
     
         8 . The watercraft of  claim 1 , wherein the stepped tunnel extends along less than half the hull length overall. 
     
     
         9 . The watercraft of  claim 1 , wherein the propeller or jet pump comprises one or more propellers. 
     
     
         10 . The watercraft of  claim 1 , wherein the hull comprises a deep vee-hull. 
     
     
         11 . The watercraft of  claim 1 , wherein the hull further comprises outboard stabilizing members mounted to hull side sheets. 
     
     
         12 . A watercraft comprising:
 a vee hull having a transom and oppositely disposed side sheets, wherein the hull defines a downwardly open stepped tunnel having a forward end defining a step and an open aft end;   an inboard engine disposed in an engine compartment near the transom;   an outdrive assembly comprising (i) a first drive shaft drivably connected to the inboard engine and extending through the transom, (ii) an upper gearbox disposed outboard of the transom that engages the first drive shaft, (iii) a second drive shaft that engages the upper gear box and extends downwardly, (iv) a lower gear box that engages the second drive shaft, and (v) a propeller or jet pump drivably connected to the lower gear box; and   a vent that provides a flow path from the stepped tunnel to an atmospheric vent port;   wherein the propeller or jet pump is disposed directly aft of the stepped tunnel.   
     
     
         13 . The watercraft of  claim 12 , wherein the stepped tunnel has a maximum width that is between 25% and 60% of the hull beam. 
     
     
         14 . The watercraft of  claim 12 , wherein the stepped tunnel has a length between 10% and 25% of the hull length overall. 
     
     
         15 . The watercraft of  claim 12 , wherein the vent comprises a plurality of channels, each channel having a first port near the step and an atmospheric port. 
     
     
         16 . The watercraft of  claim 12 , wherein the outdrive assembly is pivotable to move the propeller or jet pump between a lower position wherein the propeller or jet pump is disposed directly aft of the stepped tunnel, and an upper position wherein the propeller or jet pump is disposed away from the stepped tunnel. 
     
     
         17 . The watercraft of  claim 12 , wherein the stepped tunnel extends along less than half the hull length overall. 
     
     
         18 . The watercraft of  claim 12 , wherein the propeller or jet pump comprises one or more propellers. 
     
     
         19 . The watercraft of  claim 12 , wherein the hull further comprises outboard stabilizing members mounted to hull side sheets.