Congrats on getting a new boat.
You ever have an 454 olds in a boat before?
Its my understanding that you don't ever hold it wide open for long periods of time.
Yes there is possibilty of water in fuel due to water coming in around the fuel caps. Water seperator will help, but check seals around caps.
Also olds seem to always have oil probalems so pay attention to the oil levels.
Just my .02. lol