Yes, they will try. Even without registering in another country. My friend left Australia with an Australian registered boat, and sailed around the world for 17 years, when he got back they tried to make him pay the
import duty and whatnot. Reasoning was, they thought lot of new
equipment was added and goods bought outside of Au. He said no. Luckily, the border patrol had a
photo of his boat when it was new, so he just had to show them around the rusty
hull and the
deck with holes here and there and all the wear and tear. They let him go.