An invention relates to a marine propulsion device

Now,I'd like to introduce an invention which relates to a marine propulsion device.It has a propeller and a shaft for this propeller, which shaft is made from a unitary body of surface hard steel material(like we always used in hard steel shaft) and has its inner or forward end connected to driving means in a lower housing and its outer or rearward end extending coaxially into and drivingly carrying the propeller.

The outer or rearward end is protected by a sea water resistant sheath.

In modern outboard motors and inboard-outboard drive legs the propeller shaft is generally made bimetallic, i.e., its inner end is made of a surface hardcarbon steel material(like we always used in hard steel shaft) making this part of the shaft adapted to be surface machined for the bearings of the shaft and to carry its driving gear wheels, whereas the outer end of the same shaft, which end carries the propeller, is made of a corrosionresistant or sea water resistant material, e.g. stainless steel. However, such a construction tends to be undesirably expensive.http://www.seekpart.com/general-mechanical-components/shafts/hard+steel+shaft.html