Purpose of this screw on top of gas tank cap

brooksville_rebel

brooksville_rebel

Petty Officer 1st Class
Joined
Aug 12, 2011
Messages
240
Okay
Noticed a screw on the top of my fuel tank cap. I guess its for pressure release or so I assume. If so when should it be open (screwed out) and closed (screwed in) ?
And if the tank is not full can it be left closed or should it still be open. ? Live in Florida with the hot blazing sun and hate to blow up my boat cause the tank over pressurized (if possible to happen).

Also I have tried to find a new one since the gasket in this one is about gone but the local Marinas didn't have one and didn't notice one at West Marine. Any were else that might. ? Is one size fit all.

Attached is a pic of the cap and the fuel tank. Its not metal either if that matters.

Thanks
Mark
 

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R

rbh

Fleet Admiral
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Re: Purpose of this screw on top of gas tank cap

Breather
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Purpose of this screw on top of gas tank cap

The vent is to prevent the tank from Collapsing as the fuel is sucked out by the motor.
The tank will NOT "Blow UP" from the pressure.
They are designed to handle the strain.
Keep it closed unless you are using the fuel.

If you leave the vent open in the hot sun,
The bottom of the boat will fill with the escaping fumes and increase the risk of "Blowing UP" the boat if any spark were to happen.
 
Grub54891

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,915
Re: Purpose of this screw on top of gas tank cap

Just buy a new cap,finding a new gasket might be hard to do. Dont screw it down to tight,many do and the go south pretty quick. Just snug to keep rain out and fumes in. Loosen when running.
Grub
 
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