My boat tank fill is on the top of the stern deck. The filler cap has a
tight seal with just two very small vent holes in it. My inspection
cover appears water tight because the rain water sits in this area
unless I take it out with a sponge.

My floor fuel tank is about half full 20 plus gallons. There is a
considerable amount of water in the fuel. Enough that the boat will not
start. It will only run fine from a portable tank.

Where can water enter the fuel system ?

Lastly. will a large amount ( many bottles) of dry gas treat the fuel
so I can burn it off before taking the boat out of the water.

I am in NJ and we still have great boat weather during the day. The
boat uses to much fuel to use the small portablee fuel cans.

thanks

sonofadocker