I run new wires on my new variable speed from the back to front on a 17' boat, I used a 50 amp breaker at the batteries and #6 wire all the way from back to front, and hard wired my tm to this instead of the plug in, and not had any problems at all..... but I have 24V set up if you have just one 12V you could use #8 wire... and will work great.......