what is your motivation? You want to change careers? Or it is just an interest of yours?
The reason is important, because changing careers will be tough on you, there is not exactly a big demand for navel architects that do yacht design. Most of them, even well established ones, often have other jobs they do to support themselves when work is slow. You will also have to be willing to move to find work, and your first salierd job, if you can find one, will likely be working for a large commercial boat yard doing large steel hulls. That is where the demand is, if there is any at all.
If you love the idea of yacht design you can study is as a hobby, and perhaps design a small sailboat you can built yourself to get some hands on experiance and get a better feel for design vs. reality. Either way, there is not a lot of income to be earned designing or building small boats.