Electrical Issue questions???

Ok, i have a problem i dont have time to evaluate right now.. Once i do have time, i want to know what to do right..

Ok, so my brother took the mosca and put it at his house during the storm since we were out of town.. During saturday nights rain and sundays rain it rained so much that the boat hull was completely filled to the top with fresh water.. My brother didnt realize it, but he said that my lights were on on the boat and the switch was lit up, but it was not on... So i told him to look in the hatches.. They were full of water.. So a ground out i suppose.. I had him drain the water and turn the perko switch to off etc..

So, what should i do to test this out once it is dried out etc aside from turning everything on... I just dont want to burn anything up etc

Thanks

Thomas