Fuel Vent spurting and fill up.

M

Morgan Jane

Active Member
Sep 10, 2010
422
Occoquan, VA
Boat Info
2008 55 Sundancer
Engines
Man 900's
My last boat was a 48 Sundancer, If I wasn't paying attention when filling the tanks, when the tanks got full, fuel would spew out the fuel tank vent line openings out the side of the boat. Has there been a solution to this issue? Can you momentarily valve that line off and redirect the vent line to the opposite tank? or to a catch can? There has to be a solution. I don't necessarily have to top off the tanks, but dumping fuel into the tributaries where I boat can be a big issue and I would like to eliminate any possibility. Any ideas?

Morgan Jane
 
Mine does the same thing....eventually I learned I can listen and you can tell when your getting to max full...it took a few spews doing it myself...but you can hear it
 
The "free" answer is to listen closely for the "gurgling" sound. As the tank gets full, fuel will back up (go into) the vent line faster than the fill line because of the size difference. If it's hard to hear, you can install a "whistler" in the vent line - easy cut and splice. This is kind of like those things you had as a kid that were the size of a lipstick tube and you could blow into them or suck through to make a whistling noise. As you're fueling, air is rushing out through the vent line and will cause the device to whistle loudly. As the tank approaches full, the amount of air rushing out will diminish, as will the whistling sound. I have one of these on my Grady and it works great. Although I don't have personal experience with it, you could also check out the Racor fuel/air separator as it's supposed to make automatic fuel nozzles turn off like it does with a car.
 
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I just happened to be looking at the Racor solution, it's actually a fuel/air separator that goes into the vent line. Here is the link: https://www.parker.com/literature/R...-_LifeGuard_Fuel-Air-Separators_-_RSL0184.pdf.
Looks like they can be had for about $100 each.

I have also used these attached to the fuel vents:
41TZtRxipYL._AC_.jpg

Our club's fuel dock has them and they are required during refueling. But, I just did a search and they appear to be discontinued. Not sure why, perhaps liability?
That said, agree that practice and careful listening will largely allow you to tell when it's getting close.
 
My 330 does that all the time. We are not allowed to self-fuel at our marina so the staff do the fills. I warn them each time that once the levels are getting close to full, then need to listen carefully. If they wait till they hear a gurgle its too late. Its already spilling out the vent. They need to listen for a subtle change in the sound at the fill. As soon as they hear the sound change, they need to stop. Its really subtle and if its noisy at the fuel dock, they miss it and spill. I wish there was a better solution.
 
Creekwood said:
My 330 does that all the time. We are not allowed to self-fuel at our marina so the staff do the fills. I warn them each time that once the levels are getting close to full, then need to listen carefully. If they wait till they hear a gurgle its too late. Its already spilling out the vent. They need to listen for a subtle change in the sound at the fill. As soon as they hear the sound change, they need to stop. Its really subtle and if its noisy at the fuel dock, they miss it and spill. I wish there was a better solution.
Click to expand...
I'm surprised your facility won't let you do the fueling. EVERY place I've gone REQUIRES boaters to do the fueling. The most they will do is hand over the pump. I always assumed it was for liability reasons.
 
alnav said:
I just happened to be looking at the Racor solution, it's actually a fuel/air separator that goes into the vent line. Here is the link: https://www.parker.com/literature/R...-_LifeGuard_Fuel-Air-Separators_-_RSL0184.pdf.
Looks like they can be had for about $100 each.

I have also used these attached to the fuel vents:
41TZtRxipYL._AC_.jpg

Our club's fuel dock has them and they are required during refueling. But, I just did a search and they appear to be discontinued. Not sure why, perhaps liability?
That said, agree that practice and careful listening will largely allow you to tell when it's getting close.
Click to expand...

I'm liking that Racor device. When fueling my new boat on the trip north, I found that even with moderate speed fuel pumps there was some fuel blowing out of the vent. The only way to stop it was to slow the pump way down.

I also found a tendency for the fuel fill to "burp" near the end, spewing fuel all over the deck. Oddly, it was worse if I shut off the fuel flow quickly. Releasing the trigger slowly caused less / no burp spray. Most annoying was on my 3rd fill up of the trip. I had managed to not spill a SINGLE drop of fuel. I let the nozzle sit for a minute to drip, then handed it to the dockhand. I came back to install the fuel cap and found the tank had burped all over the deck.
 
Why would you want to fill it to the very top. Expansion will cause the fuel to exit the vent.If you know your tank levels say 1/2 is 50 gal used then only add 45 gal.
 
Just to reiterate... that inexpensive "whistle" is fantastic. You'll get funny looks from bystanders, but it's VERY easy to hear, even in a noisy environment. And you can easily notice the change in whistle "intensity".

Brad, check your vent line - it's possible that it's got a low spot or a horizontal run that is collecting fuel, which could lead to that burping. Although, it could just be a combination of where the vent is plumbed into the tank, hose length and fuel sloshing. Also, look to see if there's an "upward loop" just before the hull fitting. If not, adding that might help.

Or... This is another thing I've never personally used, just something that I'm aware of... look up Attwood fuel vent surge protector. It has a little check valve in it that will be closed ONLY by fuel, not by air.
 
b_arrington said:
I'm liking that Racor device. When fueling my new boat on the trip north, I found that even with moderate speed fuel pumps there was some fuel blowing out of the vent. The only way to stop it was to slow the pump way down.

I also found a tendency for the fuel fill to "burp" near the end, spewing fuel all over the deck. Oddly, it was worse if I shut off the fuel flow quickly. Releasing the trigger slowly caused less / no burp spray. Most annoying was on my 3rd fill up of the trip. I had managed to not spill a SINGLE drop of fuel. I let the nozzle sit for a minute to drip, then handed it to the dockhand. I came back to install the fuel cap and found the tank had burped all over the deck.
Click to expand...

I took a couple weeks trip last summer. At each stop I topped of the fuel. When I would get to about 80% full, the fuel would come out of my vents no matter how fast we filled the tanks.

I ended up removing the vent line hoses at the fuel tank (2 per tank) and blowing some compressed air through them. There was a whole bunch of stuff that came out of the hoses including a few bees.

Haven't had a problem after this.
 
Two typical problems fueling, 1. vent overflow 2. splash back at the fill pipe

Newer boats have fuel system and vent modification that prevent this. Cross tank venting with internal ulage valves (or FFV -Fill Limit Valve).
As the tank nears 100% fill, and depending on angle that may be before the 100% capacity, the tank vent fitting goes under liquid and fuel can spit out.
A ulage valve prevent over filling the tank greater beyond 90%, since we cant see how full the tank is this is what leads to most problems.
The valve closes at 90% or less allowing for expansion. And when it closes fuel/air vent out the fill pipe which should shut off the nozzle.

A second device in the fuel fill line helps with prevent a large rush of air and fuel backing up the fill pipe and splashing/spitting.
http://perkofuelsystems.com/system_design/


Some of these can be retrofitted to our older boats.
I have purchased but have not yet installed these devices. I'll report back on how difficult and how effective at some point.
1. Vent line valve, contains a float that closes the vent by 95% (not completely) if liquid enters the vent line.
You mount it vertically as low as possible in the vent line. But above the tank top. $13
https://www.greatlakesskipper.com/lund-1988549-black-4-3-4-x-2-1-2-inch-plastic-boat-fuel-vent
or this
https://www.perko.com/catalog/fuel_system_components/759/in-line_vent_hose_surge_protector/

2. Inlet Check Valves - Flapper Valve - Fuel fill , $12
https://www.perko.com/catalog/fuel_...plication_inlet_check_valves_-_flapper_valve/

And I may add fill limit valves
https://www.perko.com/catalog/fuel_system_components/873/nptf_threaded_fill_limit_valves/
 
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Bt Doctur said:
Why would you want to fill it to the very top. Expansion will cause the fuel to exit the vent.If you know your tank levels say 1/2 is 50 gal used then only add 45 gal.
Click to expand...
I do it once in the spring to get the tanks even again... I am notorious for forgetting to switch the generator from right to left
 
Creekwood said:
My 330 does that all the time. We are not allowed to self-fuel at our marina so the staff do the fills. I warn them each time that once the levels are getting close to full, then need to listen carefully. If they wait till they hear a gurgle its too late. Its already spilling out the vent. They need to listen for a subtle change in the sound at the fill. As soon as they hear the sound change, they need to stop. Its really subtle and if its noisy at the fuel dock, they miss it and spill. I wish there was a better solution.
Click to expand...
What's the law about the discharge of oil in Canada? Is it like the U.S. where one drop might result in a violation?
 
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