That's good information. Unfortunately, where I want to put it, it would be very difficult to insulate the area so the heat tape works effectively.
OK, Mr Pearson, several of us have been trying to give you the "HINT".
Since you haven't taken it, here is the BLAST.
BOATS ARE NOT DESIGNED TO BE LIVED ABOARD, IN FREEZING TEMPS. PERIOD!
IF YOU'RE BENT ON KILLING YOURSELF, OR SINKING YOUR BOAT, YOUR CALL!
There's good reason that almost 100% of boat owners would never attempt what you're attempting.
Learn from others. Don't attempt to re-invent the wheel, especially since you don't appear to even understand what that "WHEEL" actually is.
I'm done with you.