Minn Kota 24 volt saltwater motor. Digital display shows batteries are fully charged but nothing happens when I turn the stick. Any ideas where to start troubleshooting?

Start by looking at the wiring, check voltage in the top where the battery wires come in, then check with it turned on. If voltage falls, you have a wire/connection problem.
John

Thanks John, I'll do that tonight, do I need to remove the motor from the boat to do that? Remove the cover for the tm?

call minnkota tech support, they're free

Well I took the motor off and hooked it up to my lawnmower battery (12v) and it ran... So I think it's a battery issue as when I pulled the batteries only one battery will take a charge, when I hook charger to the second battery it says "check connection" leading me to believe the battery is shot.

Question now is should I replace both batteries together or will there be problems if I only replace the one? Batteries bought new in October of '09.

If they are that old I'd replace them both, and not with wallmart batteries

I think theres a place that sells used or "re-cored" batteries in my area. I'm sure brand new batteries are better, they sure are expensive... Has anyone ever used these re-cored batteries before and how long do they generally last?

Buy you some good batteries and be done with it. If you can't afford to replace both right now buy one to replace the bad one and buy the other when you can.

Stay away from reconditioned batteries. You may find "factory blems" which are OK, but stay away from reconditioned.

You may want to consider checking the manual on your battery charger. Some brands of on-board battery chargers will not charge a battery if drops below 8 volts. Yet you can connect the battery to a stand alone battery and often times it will charge. Still doesn't mean it's a good battery worth keeping, simply trying to isolate the logic built into your battery charger.