Fuel vent problem, help

Livetosea · #1 06-13-2013, 11:19 AM

Is it possible that I have a clog in my fuel vent? While filling tank on trailer last week and thinking the tank was only 3/4 full; fuel started spirting out of fuel (location) vent high on port side underneath filling cap. I tried to start filling very slowly afterward to see if the problem was me filling too fast but, same thing happened. I have read here in the forums in the past that some people have had wasps getting into the vent that created that problem. If I want to check to see if that is the problem how do you go about checking or removing the vent at hull side? I don't have access from the inside. If the vent is clogged up with some kind of wasp or whatever, will fuel still come out of the vent?
The next morning I was smelling around my stern hull vent and there was a heavy fuel smell. A little nervous.
Thanks for any input.

Bushwacker · #2 06-13-2013, 02:12 PM

The better quality vent fittings have screens in them to keep critters out. You don't say what model boat you have, but you may have to install an access plate in the inner liner adjacent to the fuel vent/hose fitting.

What's more likely is that when boat is on the trailer, the vent fitting may not be at the highest point on the tank, so you're trapping air in the tank and it'll start spitting fuel out the vent before the tank is full.

On my Seafari the fuel fill is on the starboard side a couple feet fwd of transom, so if I"m refueling at a marina, the boat would be healed to stbd and down at the stern a bit since that's where I'm standing. The highest point on the tank is at the front on the port side, so that's where they put the tank vent (tank is original), with vent hose running from there to the overboard vent fitting in the hull back near the fill pipe, so you can tell when it's getting full. However if I refuel at a gas station with the boat on the trailer, the front of the tank is indeed lower than the rear and it evidently traps air in the tank, because even though it spits gas out the vent and tries to overflow at the gas station, once I get it home and jack up the front of the trailer, I can always add about another 5 gal before the tank is actually full. Sounds like you might be having the same problem! I just take a 5 gal. jug along when I get gas so I can top off at home or after I launch the boat.

Livetosea · #3 06-13-2013, 03:32 PM

Bushwacker,
Thanks for the advice. Mine is a 1984 23' CC. That could very well be the problem I am having. The bow seems to be lower while on the trailer which could be trapping air towards the back of the tank. I am thinking the reason why I was smelling fuel fumes in the bilge through hull vents the following day is because, I had the fuel all the way up the fill line and probably a slightly loose fitting towards the top of the fill cap? Great idea on cutting and installing an access plate in the inner liner adjacent to the fuel vent/hose fitting, brillant!!

Thanks

Bushwacker · #4 06-13-2013, 09:41 PM

Next time you use the boat, take a carpenter's level or a combo protractor/level with you and compare the angle of the deck with boat in the water to what it is on the trailer. Gas fumes in the bilge are not good! You might also want to check the sending unit gasket on the tank too to make sure it's not leaking. You can seal it with the old No. 2 Permatex (don't use silicone . . . it's not gasoline resistant!).

bigeasy1 · #5 06-14-2013, 09:07 AM

I've had a couple fuel problems over the last couple of years.Once being when I was filling up at a gas station.I started pumping in gas and after a couple of seconds,fuel started backing up,and came shooting out of the deck fill,covering me in gasoline.It was a scary experience.
In my case,it turned out to be a spider that made his nest in the fuel vent.The vent did have a screen on it,but that 8 legged critter had his silk embedded into the screen.We cleaned the vent and it was good from then on.

The second was a bad sending unit gasket as mentioned by Denny.I was getting this strong odor of gasoline below the decks every time I filled the tank at the marina.I couldn't figure out where it was coming from,checked all hoses,clamps etc.It wasn't until i looked at the fuel gauge sending unit from a slight angle. I could see a dried up halo like stain around the sending unit.
I ended up replacing the whole unit with a new gasket,and it solved the problem.Looking straight down on the unit didn't show any stain or leak,but it showed up when looked at from an angle.
I only had the issue when I filled the tank,so like you it had to be something like Denny mentioned, either the angle of the boat when filling it or a bad gasket.Denny also recommended the #2 permatex to me,so I did use it,but very sparingly and so far it's good,no more fuel odor.

Livetosea · #6 06-14-2013, 01:32 PM

Bushwacker- I filled boat with fuel this morning on trailer and no vent problem nor fumes in bilge so, I am thinking that the problem is angle of the tank while on the trailer. Tank was only 1/2 full before pumping 20 gallons this morning. I will use the level to see the difference in angle. I had a brand new sending unit installed 2 years ago when hanging new 250 4 stroke Yamaha don't think that would be an issue (I will check though). I am going to cut a access plate in order the check hose clamp at fill cap. I think that maybe when I had fuel backed all the way up the fill hose that there might be a loose fitting around cap?
bigeasy1 - I will look for insects clogging vent too. A few months ago noticed motor pisser wasn't pissing from the cooling system tube; stuck a wire into see if anything was clogging it; a little something came out and water started pissing again. Whatever it was that crawled up there sure smelled horible on the end of my finger when it came out!!

I'll be sure to use someone elses finger this time when I check the fuel vent.

Thank you both.