One of the best upgrades to small fishing boats is replacing the 12-volt trolling motor with a more powerful 24-volt model. In addition to producing more thrust, this upgrade will also let you spend more time on the water, as the combination of two trolling motor batteries will last much longer before charging is required.
Determine a suitable location for the battery tray for the added battery. If possible, try to mount the tray where the weight of the two batteries is evenly distributed side to side in the boat.
Install the tray in the boat using stainless steel wood screws 3/4 inch long. Make certain the tray is in a location where the screws will not protrude through the boat hull.
Secure the added battery in the tray.
Attach the red wire from the old 12-volt system to the positive terminal of the first battery,
Attach a battery cable from the negative post of the first battery to the positive post of the added battery.
Attach the black wire from the original system to the negative post of the added battery.
Remove the 12-volt trolling motor from the boat and mount the new 24-volt trolling motor.
Plug in the new trolling motor into the original trolling motor receptacle.