One year old pontoon boat corroding totally away

My name is Frank Gregory I bought a G3 22' tri toon a year and a half ago, it has spent 6 months in the water. My grand kids love it but the boat is rotting away, electrolysis is eating up the boat. I had a dual battery system put on with a Percko switch. The pontoons are pitted from front to back and the wall between the changing room and engine area where the batteries are is corroded away 2" up from the floor, you can put your hand through. The dealer says it's up to G3 but G3 says if the dealer installed the dual batteries wrong it their responsibility. How can this much damage happen in only 6 months in the water. The Perco switch is mounted on the wall that is eaten away. How can I go about proving where the electrolysis is coming from. I am sending pictures.

       

Thank you,