Welcome to iboats most likely it will be under the CC floor you probably find a round cap access panel to the fuel sending unit the tank it self is sandwiched between the hull and the floor what are you trying to do?
I dont think he wants to use an impact driver cause u may cause a few sparks. And that might not be such a good thing when working around a gas tank.
Heres what I used on mine and I use on all rusted screws and nuts. Go to a local auto parts store and ask for valve grinding compond. Put alittle on the tip of the screw driver or socket and it will prevent it from slipping.
