Inadequate Gas Tank Venting

[twarren]

I have an Evinrude 9.9 that has a problem with pressure that builds up in the gas tank. When the tank sits and is attached to the motor the pressure builds up, expands, and distorts the tank. The pressure has been so great that the fuel line at the bulb now leaks gas. Is there a venting issue, or is this normal? Am I supposed to remove the tank and crack open the cap after every use. Thanks in advance for any suggestions.

[boats.net]

If there is excessive pressure that is definately a venting issue. If you have a portable tank it is recommended you remove it from direct sunlight to keep evaporation to a minimum. However the vent must be open.

[twarren]

Quote:

Originally Posted by boats.net If there is excessive pressure that is definately a venting issue. If you have a portable tank it is recommended you remove it from direct sunlight to keep evaporation to a minimum. However the vent must be open.

Where would this vent be located. Is it on the 6-gallon plastic tank, the hose ***embly, or part of the engine. When I open the cap, air rushes in and the distortion in the tank goes away. I know that there must be a vent somewhere, but I ma unsure exactly where it is. Thank you for your help.

[boats.net]

The older metal tanks vented where fuel hose connects to tank, hose connector pushes in the vent valve to vent when connected to tank. The plastic tanks had a vent screw on gas cap and should be opened to vent.
The new EPA tanks have a pressure release valve(some have manual vent screw as well as pressure valve) but may always have a little pressure in it.