Prototype/constructor switch now working as expected. There actuall was never a problem with linking the JS to the HTML file. Rather, the issue was that I was testing a copy of the HTML file residing in the incorrect directory.
Test for self-referencing constructor for CarBoat() set up. Not yet tested.
Calling CarBoat.prototype.constructor after setting CarBoat()'s constructor to an instance og itself is returning an *unexpected identifier* error. Will try setting it to own-class instead.