I've had to take the fuel hatch cover off several times due to a couple of bad sending units, and another tnat leaked.I had used marine silicone, and although I pretty much think that silicone has no place on a boat, in this case I think its okay.
It does collect dirt easily, but its effective in sealing out water, and when the hatch needs to be pulled, its easy to break the silicones bond.
God help you when you have to break the bond of 5200.When they say its mostly for permanant repairs, they mean it.
Sika corp also makes several marine urethanes under the Sikaflex banner and offer a couple that are considered removable.They may be better suited for your needs

Sika is fine.

I used GE silicone and had no leaks. It was also easy to remove when I had to check my sending unit.