I am setting my back trolling motors up on bigfoot switches.  Can I run both motors off one switch or do I have to run each one individually.  

Also, if I tie my batteries together, can I run both 12V motors off them?

Or am I making this more complicated than neccessary?  

I just went and priced 6 gauge wire, and I will be sleeping on the couch if the wife finds out how much I am wanting to spend...  :-/

Also, will 12 gauge work to extend my Depth Finder wiring 4 ft.  to reach the battery?

I take it you have 2 T-motors on the transom. Unless they are high thrust I don't see why you couldn't tie them together on 1 bigfoot switch just as long as the amps don't get to high. If you wire your batteries parallel you still keep them at 12 volts just with 2 batteries now.

Thank you for the info.  Yes, I have 2 50 lb.  Minn Kota motors on the back.  I have went and exchanged all my batteries at Wal Mart, so they are all fresh and the same date.  I only use the back motors, going from place to place, have a bow mount for actual fishing, so they will be used basically at the wide open, fastest setting at all times.

You could tie them all together and run them off on switch and batteries. However with 12 volt TM on high, ( I have a 50MK know how it is) you might be pulling a lot of amps and burn up the switch also you might run down your batteries faster if all tied together, because of the high amps. I know on my small boat Have a 52 up front and a 50 out back, they each have their own battery. I used to put them together, but when running both at full power the battery life was cut short. just my experience.

The 12ga wire should be more that enough for the DF, have you ever looked at how small the wires are they use? must be 20ga or smaller.

How much is 6ga wire now? You know since your using only 12volt TM's you could use 8 ga with no problem. I know that is what I use on my small boat with 12 volt TM's is 8ga, on my big boat I have a 36 volt TM and it calls for 6ga. well I ended up using 4ga since it was cheeper than the 6ga when I bought it. I did find out one thing the 6ga wire the factory has installed on the TM is way smaller that any 6ga I have even seen, even  smaller than the 8ga I have. I have run the 36volt TM on my small boat with the 8ga and have no problems.

You definitely don't need 6 gauge if the batteries are at the same end of the boat as the motors. 6 gauge is recommended for a long run from the back of the boat to the front.

Well, I have to run from the motors to the front of the boat, to the bigfoot switches, then back to the batteries.  So all told, it will be 20 ft. of wire for each motor.... so I was thinking 6 ga. so as not to lose so much.

I would use a starter solenoid as a contactor use big foot swich to pull solenoid in. This would allow smaller control wire for long run.