Replaceable nose section for a marine propulsion unit

Abstract

A replaceable nose section for a marine propulsion unit is disclosed. The marine propulsion unit includes a lower gear case that extends into the water and includes a lower portion that includes a shaft section, a prop section, and a nose section. The shaft section defines a first volume. The nose section includes an intermediate section that includes an intermediate bulkhead that defines a second volume. A nose cone is threaded to the intermediate section and defines a third volume such that the first and third volumes are not in fluid communication.

what is claimed is: 
     
         1 . A marine propulsion unit comprising:
 a lower gear case having a lower portion, the lower portion comprising:
 a shaft section defining a first volume and having an aperture on a front end; 
 a prop section located abaft the shaft section; 
 a nose section located forward of said shaft section comprising:
 an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being engaged to said aperture; and 
 a nose cone defining a third volume and engaged to said intermediate portion; 
 
   wherein said first volume and said third volume are not in fluid communication.   
     
     
         2 . The marine propulsion unit of  claim 1  wherein the lower portion is torpedo-shaped. 
     
     
         3 . The marine propulsion unit of  claim 1  wherein the lower gear case forms a portion of a strut that extends below the hull of a marine vessel 
     
     
         4 . The marine propulsion unit of  claim 1  wherein said intermediate portion is threadably engaged to said aperture and said nose cone is threadably engaged to said intermediate portion. 
     
     
         5 . The marine propulsion unit of  claim 1  wherein said prop section comprises front and rear counter-rotating props. 
     
     
         6 . The marine propulsion unit of  claim 5  wherein the front prop has three blades and a first diameter and the rear prop has four blades and a second diameter that is less than the first diameter. 
     
     
         7 . The marine propulsion unit of  claim 6  wherein the blade area of the front prop and the blade area of the rear prop are substantially the same. 
     
     
         8 . The marine propulsion unit of  claim 5  wherein the front prop has four blades and a first diameter and the rear prop has five blades and a second diameter that is less than the first diameter. 
     
     
         9 . The marine propulsion unit of  claim 8  wherein the blade area of the front prop and the blade area of the rear prop are substantially the same. 
     
     
         10 . The marine propulsion unit of  claim 5  wherein a propeller shaft anode is threadably attached to a rear prop shaft. 
     
     
         11 . A marine propulsion unit comprising:
 a lower gear case having a lower portion, the lower portion comprising:
 a shaft section having a threaded aperture on a front end; 
 a prop section located abaft the shaft section; 
 a nose section located forward of said shaft section comprising:
 an intermediate portion having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture; and 
 a nose cone threadably engaged to said intermediate portion. 
 
   
     
     
         12 . The marine propulsion unit of  claim 11  wherein the lower portion is torpedo-shaped. 
     
     
         13 . The marine propulsion unit of  claim 11  wherein the lower gear case forms a portion of a strut that extends below the hull of a marine vessel. 
     
     
         14 . The marine propulsion unit of  claim 11   
     
     
         15 . The marine propulsion unit of  claim 11  wherein said prop section comprises inner and outer counter-rotating props. 
     
     
         16 . The marine propulsion unit of  claim 15  wherein the front prop has three blades and a first diameter and the rear prop has four blades and a second diameter that is less than the first diameter. 
     
     
         17 . The marine propulsion unit of  claim 16  wherein the blade area of the front prop and the blade area of the rear prop are substantially the same. 
     
     
         18 . The marine propulsion unit of  claim 15  wherein the front prop has four blades and a first diameter and the rear prop has five blades and a second diameter that is less than the first diameter. 
     
     
         19 . The marine propulsion unit of  claim 15  wherein a propeller shaft anode is threadably attached to a rear prop shaft. 
     
     
         20 . A torpedo-shaped section of a marine pod unit comprising:
 a shaft section defining a first volume and having a threaded aperture on a front end;   a prop section located abaft the shaft section;   a nose section located forward of said shaft section comprising:
 an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture; and 
 a nose cone defining a third volume and threadably engaged to said intermediate portion; 
   wherein said first volume and said third volume are not in fluid communication.