Gas Tank Venting

[Roman]

Hi, I have a 1998 5.7m A/B. Nice boat, has a 120hp Nissan on the back. The one problem I Have is the gas tank venting. The internal Gas tank takes forever to fill. Has anyone run in to this problem and perhaps added another vent in the tank.
Thanks Roman

[Mark Halliday]

Roman

Do you mean the fuel rises up the vent and cuts off the pump when filling up?

[Roman]

Yes, It takes half a day to fill the tank.
Roman

[Scary Des]

Ave Roman
There are several possible problems here:-
You could be filling the tank up hill, in other words, the filler is below the highest part of the tank.
The filler pipe is too small or it takes a twisted route to the tank.
The baffling in the tank doesn’t work.
Or your vent is too small, too low in the fuel or blocked.
All of these are a bit of a problem with a built-in tank but you can check the last one by blowing down it.
Putting in an additional vent could help if you can get to the tank in the right place, there would be no point venting the tank at the low end if you are still getting air trapped at the higher end.
Obviously lots of care should be taken with fuel tanks especially when empty
Des

[Scary Des]

Another thing to try, while filling up, is putting a rubber hose down the filler pipe until you judge it is just above the fuel level in the tank and see if this helps If it does more venting at the filler pipe end would help. Des

[Mark Halliday]

Des (yet again ) is probably right.

I have the same problem. 2" filler and 3/4" vent pipe, both mounted side by side right at the front end of the tank.

I have found towing with a Range Rover helps.
OK that sounds daft, but the hitch is a bit higher than a car and therefore the tank is slightly higher at the front end. The other half of the boat tows with an ordinary car and has to un-hitch and jack the jockey right up.
Luckily we have a clear breather pipe which is just inside the hatch so I can see the fuel blowing back. When it does, I just ease off the pump til it drops back. Rocking the boat also helps when the tank is nearly full.

Raising the front rollers/beds on the trailer could be worth trying. (Assuming you fill to the front of the tank).

Thinking about it, none of this helps if you are filling afloat.
Try getting the crew to move around or stow the beer somewhere else.

Plan B, for some time in the future, is to put a length of much large diameter pipe in the breather to act as a damper. I am not 100% sure it will help, but has got to be worth a try.

[Roman]

Unfortunately, the tanks fills at the backand not the front. This was A/Bs approach in 1998. The boat originally also came with a water filter, but I could not get the fuel to fill it and run the motor. I had to plumb around the filter.
Thanks Roman