I recently purchased a used aluminum starcraft bassv180 with a fuel tank built in the belly of the boat. My problem is when it sits uncovered with the tounge raised and the sun beating down on the boat pressure builds up and I have gas leaking out the vent. Is this normal and should I just plan on leaving the tonge down when I know it's not going to rain? Or do I have some kind of problem with my fuel tank?<br />Thanks Jim