Context matters hugely and you have to consider both dictionary definitions and popular connotations in different areas.
The same vessel might be a "yacht" when you are talking to ships or customs
officials, or looking for a harbor for pleasure vessels, but your spouse might call it "that g$d#$!ned boat" and it may feel it a bit more like a ship when you have to pay the haulout bill or do the bottom. It turns into a little boat again when you get into big seas. And you might want to try to convince the tax authorities that it's only a dinghy