Fuel tank venting question

[w2much]

In the rear of my boat near the fuel fill is my fuel tank vent. It is about 6 inches down and to the side of the fuel fill. I put a clam shell over it to keep water from entering either by splash or by hose when rinsing off the boat. I noticed that the vent hose on the inside of the boat dropped down immediately from the vent to the tank. It did not rise and loop as it should to keep water out. In other words water that entered the vent drained to the fuel tank. The way the boat is configured there really was not any room to give the hose a good enough rise before dropping down towards the tank. I spliced the vent line , added a few feet and ran it away from the vent. At this point I ran the vent line in about an eighteen in 360 degree circle. Now when I overfill my fuel tank I get to hear the gurgling of fuel in the 360 degree loop before it splashes out the vent. Of course I try not to overfill the tank, my sender does not work. But I need to know I have a full tank when fishing offshore. My question is this:
Can this 18 inch circle in my fuel vent cause a vacuum while running. ? Or does the fuel pump overcome this air vent restriction by sucking air through the half circle filled with fuel and the fuel gets returned to the fuel tank through the air vent line.? I would guess that within this circle loop is only about a pint of overfill fuel.

 

[Watermann]

Creating the loop could be a problem, this is the way I've done my vent lines so there isn't standing fuel in the line as with a 360 loop.

 

[JASinIL2006]

I would think the loop would be a problem, too. Once fuel got into the loop, you'd get splashed when filling the tank and it seems like the fuel pump could have trouble pulling fuel at the correct pressure. My vent line is as Watermann describes, too.

 

[Ned L]

I understand your concern. From a “will it work” concern, if you have an anti siphon valve on your tank that may require more vacuum for the fuel pump to overcome than the loop. Still, the idea of a loop isn’t great as it doesn’t really “vent” the tank properly, ... ...

 

[w2much]

Thank you guys. I will take the loop out and somehow put just a half loop. Was not certain of resistance caused from the 360 holding fuel.

 

[fishrdan]

Try this type of fuel vent fitting.

I have one of them in the bow of my boat and it's been blasted by gnarly waves, with no water in the fuel. Vent line runs straight down to the fuel tank.

 

[tacx]

To answer your question. Yes, when the fuel level reaches the vent line you no longer have venting and it will create a vacuum that will give your problems.

 

[w2much]

Got it done. Thank all of you.