Do not mount your charger directly to the aluminum.......Mount it to a piece of ply wood or what I used was a heavy plastic cutting board that I bought at Walmart...I cut it the size I wanted and drilled and counter sunk some holes to bolt the charger to...then sealed over the counter sunk holes on back side with silicone...then mounted that to the aluminum. This way the charger is isolated from the boat and cannot set up a electrolisis and attack the aluminum boat.