Gas odor from internal tank vents

[jschwartz]

Hi,

I have a sweetly resored 1972 Grady White 17' dual console outboard with dual built in gas tanks below the console. The feuling inlet and the tank vents are on the rails just fore of the windshield. Their orientation is horizontal (facing the sky).

My problem is a strong gasoline odor that is coming from the vents. I have sniffed the entire feul line and tightened all clamps and I am convinced the odor is not coming from anywhere else.

So my questions is, are there any tricks to lessen the smell from gas tank vents?

Thanks,

Jamie

[alan white]

Bad design, I think, placing fuel tanks/vents there. You shouldn't relocate the vents if it means passing any portion of the vent tubes below the liquid of the tank itself.
Excess heat shouldn't be the problem, as it hasn't been that hot there this summer.
You may be stuck with this problem unless you can relocate the tanks or raise the vents to a point overhead (not easy unless you have something overhead to attach them to!).
Even a vented box (or two) aft would be preferable to what you have now. You could fabricate it easily from plywood/fiberglass and it would vent behind you. You could use the tanks you already have and use the current tank location for stowage.

[jschwartz]

Thanks, Alan White. To clarify, no portion of the vent tube passes below the liquid of the tank. Both the feul inlet and vent hoses run to the top of the tanks.

Because I feared that water was getting in to the tanks through the vents, I attached small pvc cowls over the vents, but that did not affect the gas fume odor coming from the vents. So, what if I extended the venting pathway by running PVC pipe from the cowl out to the stern? Might that help?

Jamie

[alan white]

I don't understand... you might read my response again.
I never said it was likely that any portion of your vent tubes run below the tanks top surface. I said IF you relocate the vents, make sure they don't sag below the tops of the tanks.
Water in the gas will not cause vapor to increase, it will just cause your gas to have water in it, which can make your engine hard to start, I'm sure.
You could certainly run a vent to the stern. I wonder if you could do that without having the vent tubes going lower than the top of the tanks (It might depend on your planing position. If the boat tilts enough to lower the vent tubes while underway, you could easily siphon your gas right out.
Wouldn't those PVC tubes or tube get in the way anyway?
My suggestion is you either relocate the tanks or vent the tanks differently IF YOU CAN, meaning either up a stiff small diameter pipe or tube to a point over your head or back to the stern or side just so long as you never allow the passage to run below the liquid gas in the tank.
Having your current vents face up is going to let water in. Cowls can prevent this so that fix made sense. Obviously, they'll be zero difference regarding the odor.
If it were my boat I'd attempt to get the vents up a foot above my head. I'd make the vent extensions out of stainless pipe and use the windshield frames to support them. Either that or, as said, relocate the tanks to the stern where they belong.

[jschwartz]

Yes, now I understand completely, especially that if I relocate the vents I must be careful not to let any part of it run below the liquid in the tank during any position the boat might be in. Thank you for laying out my options. It is a big help to know what they are.