Fuel vent. Open or closed?

[paulmelys]

Hi there, Can anyone tell me whether my fuel vent should be open or closed when in use? I have a Sunbird SPL 19 which I am about to go on for the first time. I used to have an old fishing boat, but now the Sunbird has a built in fuel tank with a vent cap next to the fuel intake cap, and I'm new to boating and am not sure. Please excuse my ignorance.
any help appreciated.
Paul

 

[Nautical]

Vent cap should be open otherwise you will starve the engine of fuel as the tank begins to empty. Bit like the vent cap on outboard engine tanks, its only there to stop spilage when carrying the tank. I am suprised it gives you the option to shut it off if it is a built in tank though.