Does anyone here run or have ran 2 trolling motors off of one battery?  I am talking about a 40 lb bow mount and a 28-35 lb stern mount off a group 29 walmart battery  The stern mount would only be used for the 15-30 min ride in and back running both motors for a little extra pickup.

Andy

So Andy, what is your question?

How bad does it kill the battery to run two motors simultaneously?  I have not seen a 75 lb 12volt TM, which is what mine would equate to.  I am thinking that having that much motor on just 1 12volt battery might be bad for the battery with the very quick discharge rate, or that it drastically reduces the runtime that I will get with my 40 lb bow mount.  I don't like to paddle and I don't feel like experimenting with a brand new $75 battery so I am asking the question.

Andy

You can run both motors off the battery at the same time. You will drain the battery much faster. I do not think it will hurt the battery though. Just make sure your wires are big enough to handle the current draw. My guess it will be about 75 amps with both motors running.  I have heard 1 amp per pound of thrust in a 12v motor.

You may want to get one battery for each motor. You may also want to test, with a GPS, to see if your boat actually goes faster running both motors at the same time. It may not be worth the power drain to get 1 or 2 MPH.

I really don't think that would be the most efficient way to run a pair of TM's at the same time.  Both of those motors present themselves as resistance to a battery.  The TM of least resistance will basically draw more battery potential than the one of more resistance.  I believe you'd see maximum efficiency from both motors if you ran them on seperate batteries.  That or found some way to isolate the motors from one another.

I'd go with two batteries as well.  Also just a little side note, keep your reciept for your batteries at wal-mart.  They have an 18 month warranty.  Every year, just take it back with your receipt and tell them it doesn't hold a charge, they'll give you a brand new one for free.  That way you can start every year with a fresh battery.