Fuel Breather Pipe - What diameter hose ?

[smclaren]

Hey Guys

Installing a semi-perm 75lt New Era fuel tank in the cabin of my boat. Basically something I can sit up there and use on longer trips (removable on short ones) and also to give more room at the back of the boat to fish from.

I have run a fuel line foward, also want to run a breather line (flexable hose) back to the rear of the boat.

Question is ... what size breather hose to use ?

Is there a calcualtion based on fumes created from an area of fuel and the rate needed to disperse it out of the tank ? Or what ? Is there too small a diameter to use or too big ? I am looking at 8mm .... will it be too puny ? I have no idea.

Any comments, tips, ideas appreciated.

Thanks

Steve