Alpinehigh
Did you hook up the 2 batterys in a series such as bat. A- pos. to bat. B-neg. Bat. A- neg. to bat. B-pos. Then hook pos lead from unit to Pos side of A-bat. neg lead from unit to neg side of Bat A. This will give you 12 volts other than this you will only be at 6 volts. If it still dont work you might need more juice to run the unit.
Good Luck
Cold Feet
coldfeet,
One too many connections. If you connect them this way you'll complete the circuit, and cook the batteries. You should connect the unit to the positive side of the first battery, then connect the negative terminal of the first battery to the positive terminal of the second battery. Then connect the unit to the negative terminal of the second battery.
Think of how you put two batteries into a flashlight. Positive end in first. Then the second battery connects the negative end of the first to the positive end of the second. Then the tailcap connects the negative end of the second battery to the device.
It sounds like Alpinehigh had 12 volts in the first place, if the motor was spinning. He may not have had enough amps, or there could be other problems with the unit. A sealed lead acid battery of about 6 or 7 amps (also called gel cells ) should work well. Was the transducer plugged in?
Hope this helps.
Fishrmn