Yes this may sound dumb but...,on my gas tank plastic omc

it says to shut off the vent plug when not in use,but with this

100 degree weather that tank is swelling up and when i relieve

the vent cap screw boy does it spew some fumes!Should i close the vent like the tank says or leave it open when not in use? :-?

The theory behind this is to keep moisture out of the tank.  If you vent the tank when it is under high pressure and then close the vent, it will then create somewhat of a vacuum when it cools down.  I always left mine closed and never had a problem.

btw, what lakes do you fish in NC?

From small area lakes like lake wheeler near raleigh,to gaston,kerr,falls

lake.Jordan and sharron harris are normally too crowded.With the small boat

i'm somewhat limited to where i can go.I try and stay up in the creeks

in the larger lakes like gaston and kerr.I'm going to venture toward the

mountains more to try the smallies in those lakes out there.

If the tanks are subject to much of a temp change, I would leave the vent open.  I've seen plastic tanks look like a basket ball when hot, let the pressure off so it goes back to normal and it looks like a prune when it gets cool.  I've had tanks crack with the vent closed.  

I take mine out of the boat, store it in a cool place and leave the vent open.  If I don't plan to use it for a while, I dump the gas into a can and use it in the lawn mower, I don't leave gas in my tanks over one - two months.

If the tanks are subject to much of a temp change, I would leave the vent open. I've seen plastic tanks look like a basket ball when hot, let the pressure off so it goes back to normal and it looks like a prune when it gets cool. I've had tanks crack with the vent closed.

I take mine out of the boat, store it in a cool place and leave the vent open. If I don't plan to use it for a while, I dump the gas into a can and use it in the lawn mower, I don't leave gas in my tanks over one - two months.

That sounds like good advice to me.