Using the aluminum hull for ground?

I am rebuilding an older Monark and have run across a dilemma. I upgraded the trolling motor to a 55 # Minn Kota PD V2 and would like to run 4AWG power wire from the battery in the hatch area in the aft up to the connector. Here is the challenge. There is only one open channel from the aft to the bow and there is no way I can get two runs of 4AWG through it. I am considering running one for the positive, and then using the aluminum hull for the return. I know it will work electrically, but am wondering if I am missing something mechanically about this setup. I would have to be meticulous about getting good connections both fore and aft but I sure I can do that. Am I missing anything else?

I have read somewhere that this will cause corrosion to your boat hull. Maybe others can tell you more about it and why not to use the boat as a ground. Furthermore you can bet if it was ok the aluminum boat companies would have have already did it(but they don't) to save$$$$.:twocents

Don't do it...electrolisis will eat your boat up over time....create little pin holes all over it....its a slow process but in a matter of a few years your boat will be destroyed. I run my 24 volt Terrova with 6 guage wire no problem.

I think G hit it right. I think 6 gauge is the answer.

I would not try that on that many amps. Even being meticulous the risk of a high resistance connection developing and the results are just not worth it. Electrically speaking whether A/c or D/c high resistance connections even at relatively low amperages will develop heat and corrosion problems...but when you start talking 20,30,40 amps or more its just much more serious.The arcing,heat,etc that can possibly happen are just too much. Along with the potential electrolysis aforementioned.

I wired mine to 24 V and had a un-common ground which turned the boat into the ground conductor. 1st trip 4hrs and the outboard and TM were covered with white corrosion spots. Never let your alum boat be a conductor!!!!!!!!!!!!!!

OK guys I got it. I had forgotten about the galvanic action.
I am glad I asked and appreciate the reminder.

I guess I will pull the floor up which I was trying to avoid but it appears to be the best plan of action.

And I will be running AWG#4 as that is what the manual for my TM (MK PD V2 12v 55#) specifies for a run of 15' to 20' which the cable run will be.

Again Thanks

You got it right now Clint