Should I add anything to gas for my outboard boat motor?

I just recently discovered that the reason my motor kept quitting on me the first time out was due to water in the gas. I had siphoned out some gas from the bottom of the can as suggested and it wasn't long and you could clearly see a separation of gas and water in the jar. I am going to dump all of that gas out of the can and dry out the can the best I can. When I add fresh gas to the can should I add anything to the gas? I thought I heard of something that was added to the gas for outboard motors because of the ethanol that is in the gas is hard on them. Any help on this?