Hydrolic Pump on Boat

I tried to re-solder the brushes that run the armature on a hydralic pump. The battery is pushing twelve volts, what the motor requires to run. When you test the voltage at the brushes it reads less than two volts. Is this a problem with the solder or with the wiring to the motor. The first time I solder the wires to the brushes it had twelve volts and ran the motor fine. When I mounted the motor back to the pump housing it quit running. I took it back apart and the soldered joints were still intake and the voltage off the brushes was only reading about two volts again. Could this be because of the 12 gauge wire (I think it is overkill to run twelve volts through and makes soldering to a 22 gauge wire on the brushes a pain in the butt.) Help us get the boat running agian!!!