GAS SLOSHING OUT THE VENT PORT

[anchorout]

I sometimes think I loose as much fuel as waves slosh it out the vent, as through the motor. Not good for the environment or for my wallet. If this problem has been discussed before, please point me to it as I can't find it through "search".

On other boats I would run the vent hose up high and back down to the port, but can't do that here. Has someone found a check valve to fit the hose, or should I cross the vent hoses across the boat to the opposite ports?

OR, am I the only one to experience this problem?

 

[colobear]

never heard of this problem before. you may be the only one.

 

[rogerbum]

The only time I have seen gas slosh out of a vent was when the tanks were very full and I was towing on an incline. I've seen that on other boats also. I also recall Dave saying that the first design he did of the marinaut saddle tanks were a particular problem in that regard as long thin tanks were more susceptible to changes in level at one end when the boat was on an incline. If I remember correctly, he redesigned the tanks with some baffles to fix this.

 

[C-Nile]

The only time I have seen gas slosh out of a vent was when the tanks were very full and I was towing on an incline. I've seen that on other boats also. I also recall Dave saying that the first design he did of the marinaut saddle tanks were a particular problem in that regard as long thin tanks were more susceptible to changes in level at one end when the boat was on an incline. If I remember correctly, he redesigned the tanks with some baffles to fix this.

Roger,
While I don't know about whether or not the Marinaut fuel tanks are baffled, I do run into trouble if I overfill the tanks. Fuel pours out of the tank when or if it expands. I suspect that is true for most boats with vented fuel tanks.

Rich

 

[rogerbum]

The only time I have seen gas slosh out of a vent was when the tanks were very full and I was towing on an incline. I've seen that on other boats also. I also recall Dave saying that the first design he did of the marinaut saddle tanks were a particular problem in that regard as long thin tanks were more susceptible to changes in level at one end when the boat was on an incline. If I remember correctly, he redesigned the tanks with some baffles to fix this.

Roger,
While I don't know about whether or not the Marinaut fuel tanks are baffled, I do run into trouble if I overfill the tanks. Fuel pours out of the tank when or if it expands. I suspect that is true for most boats with vented fuel tanks.

Rich

That's true of all tanks if they're filled to capacity. On any boat with long tanks (such as the saddle tanks on a Marinaut), there's the additional issue that when the boat is on an incline, the difference in height from one end to the other is greater than for a shorter tank. So depending on which end the vent is on, when the incline is down towards the vent, the gas level can rise above the vent more easily on a long tank than a short tank. I've seen this happen a number of times when a trailered boat is filled to capacity at a gas station and then the exit from the station is at an incline. A significant amount of gas can come out and the driver may not even realize it.

 

[journey on]

Whilst Journey On is a 25, I certainly have had gas come out of the tank vents while we were towing. I suspect that the only reason I haven't seen it gurgle out on the water is that we were moving too fast, or it all sloshed out before we launched. And that's at $4/gal.

A couple of random thoughts. First, there's no way to tell if the tank is full unless it spills out a vent, which is a little lower than the tank fill, since the gauge is nonlinear. That's embarrassing at the pump and expensive. So now the tanks are never full.

The other thought is that one could smell gas vapors while at the dock on a fine evening. Go ahead and laugh, but I fixed it by loosely wrapping blue masking tape around the vents. Still breaths but cuts down on the smell. Tape has to be replaced every other year.

Any one have any solutions, let me know.

Boris

 

[Bill K]

I have found that if I fill fast and have my overflow bottle on the vent so I can hear a change in sound and shut it off and it won't overflow when the gas in the tank warms up.

Bill Kelleher

 

[C-Nile]

I have found that if I fill fast and have my overflow bottle on the vent so I can hear a change in sound and shut it off and it won't overflow when the gas in the tank warms up.

Bill Kelleher

Overflow bottle -- who is it manufactured by? On my boat, I have to fill the fuel tanks very slowly and know what you are talking about regarding sound. As soon as the pitch changes, I stop filling the tank. If the tank is filled too rapidly, or to the top, the gas will slosh out of the vent.

When we first had the boat in our valet storage facility, we filled the tanks in the spring when the outside temperature was around 60 degrees. Thereafter, a hot spell in the nineties occurred, and the marina told me that gas poured out of the vent pipes. Fortunately, Les Lampman placed the fuel fills outside of the cockpit enclosure!

Rich

 

[Bill K]

Here you go, I had to trim the rubber that goes around the vent to fit under my rubrail.
I lay my ear at the top of the bottle and listen for the sound change.

http://www.tgmmarine.com/nospills/pages/products.html

Bill Kelleher

I have found that if I fill fast and have my overflow bottle on the vent so I can hear a change in sound and shut it off and it won't overflow when the gas in the tank warms up.

Bill Kelleher

Overflow bottle -- who is it manufactured by? On my boat, I have to fill the fuel tanks very slowly and know what you are talking about regarding sound. As soon as the pitch changes, I stop filling the tank. If the tank is filled too rapidly, or to the top, the gas will slosh out of the vent.

When we first had the boat in our valet storage facility, we filled the tanks in the spring when the outside temperature was around 60 degrees. Thereafter, a hot spell in the nineties occurred, and the marina told me that gas poured out of the vent pipes. Fortunately, Les Lampman placed the fuel fills outside of the cockpit enclosure!

Rich

 

[localboy]

http://www.fisheriessupply.com/attwood-fuel-line-surge-protector-1675-6

Installed these. NO more spills.

 

[Sunbeam]

A question: Is the original poster (and/or any subsequent ones) talking about fuel coming out the vent while actively filling the tanks, or fuel coming out while boating or trailering?

Due to concerns about water coming into my fuel vents (which were originally installed so high up as to preclude any sort of loop upward in the hose), I installed an Attwood "P-trap" type of vent (details in the "Sunbeam ~ 22 Cruiser" thread). So far I have not seen fuel come out the vent either while boating or towing, so I think those work for that (so far anyway!)

I have, however had fuel come out both the vent and the fill when filling the tanks, if I fill too fast (which I don't do anymore, but it would be nice to be able to fill faster). The biggest problem on my boat is with the port side tank. I believe the reason is the "dog leg" in the fill hose due to the lazarette being in the way of a straighter run. But too, I can get fuel out the vent or fill on the stbd. tank when the tank is near full and it "power sloshes" as it comes in the fill hose and hits the fuel in the tank causing turbulence. Filling slowlly on the stbd tank (and extremely slowly on the port tank) cures both issues, but... is a pain.

If I had it to do over again I would cut a section out of the wall of the port lazarette and add a fiberglass "shape" (that I would pre mold around a hose/board) to re-build it, to allow that hose to run straighter without the extra dog-leg; it's not space I would miss in the lazarette, and due to being out of sight would not need to be cosmetically perfect (i.e. it is not a gelcoated exterior place). I may still do that at some point - time will tell.

Will look at the surge fittings too - thanks for the link (although they would presumably not affect the fill itself, but only the vent).

Sunbeam

 

[AstoriaDave]

Sunbeam,

Probably this is not an issue for your boat, but on mine, I discovered the tanks were dead level when the boat and trailer were hitched to my pickup, if the fueling station platform was also dead level. Some are not, and the ones running downhill towards the bow cause premature overflow and incomplete fills. I installed one of those small RV spirit levels adjacent to tbe helm, and jack up the bow a bit when needed. Only need a small plastic cup at the vent to catch any overflow, now. Same cup I use to measure out my blue Stabil.

 

[Sunbeam]

Good information, thanks.

Right now (at least) I have a "plus" in that after installing my new fuel tanks, I cut out the new fiberglass cover panels (like on the newer boats) but didn't install them (yet). The main reason was that I wanted easy access to the shims I installed between the tanks and the cleats (the tanks "grow," especially when new). So I made a set of canvas covers temporarily. The side bonus is that I can easily flip them aside and see not only the fuel level in the tank, but also the area where the fuel fill goes in (that's how I could see what was happening with the turbulence). Actually, now that I have them, I"m not sure I don't just want to make a nicer set of fabric panels instead of putting in the gelcoated ones - decision to be made later, I guess.

Sunbeam

PS: For anyone putting in new tanks: I read the advised figures on the Moeller site and followed them to the letter (they tell what percentage of length and width to allow for expansion). The expansion room looked huge, and I even debated whether it was all going to be needed. But I stuck to what they advised. Well, they certainly do expand! I would not have wanted any less of room than what they call for. It's easy to see why the original cleats were compromised original tanks appeared to have been installed "tight" to the original cleats when the boat was built).

 

[Will-C]

I put whistles that Defender marine sells that get installed in your fuel vent lines. As you fill your fuel tank the air exhausted makes the whistle,whistle. When the whistle stops the tank is full. No need to blow fuel out over the place. They work pretty well and are easy to install and not that expensive. The gas jockeys get a little worried though when they hear the whistles and they think something is going to blow up.
Normally fuel storage tanks are under ground. The underground temperature is about 58 degrees. Put in you boat on an eighty degree day and expands as it's temperature increases. I used to fill up my tanks in the late fall when the temps we in the 50's. The first warm day 65 degrees or so fuel would be dripping out the vents. I bought a fuel pump so I can pump out some fuel leave a little room for expansion and use the extra fuel in my car if I top off before closing the boat up for winter. Mr. Gasket makes reasonable 12 volt electric pumps just for this purpose. My fuel filter has an extra place for an additional fitting that you can use it to empty or reduce the fuel levels in your tanks.
D.D.

 

[Sunbeam]

I put whistles that Defender marine sells that get installed in your fuel vent lines. As you fill your fuel tank the air exhausted makes the whistle,whistle. When the whistle stops the tank is full. No need to blow fuel out over the place.

I'm still not sure what the OP's situation was (were they emitting fuel underway, on the road, or while filling), but when I had the fuel come out the vents on my boat, the tank was nowhere near full. What I believe happened was that turbulence - either in the hose or coming back up from the fuel surface in the tank - somehow blocked things and thus allowed fuel to come out the vent. Hard to know exactly what happened (it happened quickly), but the tanks were not full. I have since filled more slowly (especially after they are half full or so) and have not had the problem recur, but it's a pain to have to fill that slowly.

I didn't get anything at the Fisheries link, but I can see it was to an Attwood product so when I have better Internet I'll look it up via Google.

 

[anchorout]

I have Atwood vents on my boat. Doesn't help. I noticed after filling the tanks and trailering the boat that gas was dribbling out the vents. Also, after running the boat in swells, both tanks were less than full, indicating gas was sloshing out both vents.

It's not surprising, as my tanks are without baffles and the vents are only 6" or so above the top of the tanks with a straight run of hose. As the boat rolls or bounces, gas is rammed out the vents.

One easy solution would be to only partially fill each tank, but...

 

[Sunbeam]

I noticed after filling the tanks and trailering the boat that gas was dribbling out the vents. Also, after running the boat in swells, both tanks were less than full, indicating gas was sloshing out both vents.

Okay, I understand now.

I have Atwood vents on my boat. Doesn't help....It's not surprising, as my tanks are without baffles and the vents are only 6" or so above the top of the tanks with a straight run of hose. As the boat rolls or bounces, gas is rammed out the vents.

Just curious: Do you have the Attwood "P-trap" type vents? Or just "regular" vents (I believe they make both?).

I had regular vents (not sure what brand, maybe Sea Dog), and it sounds like they may have been set up similar to yours. That is, mine ran "straight" up to just under the gunwale, and attached directly to the vent fitting (which had a 90º bend but no upward loop and no way to add one due to their height).

Will-C advised of some P-trap vents that he had installed, and at first I thought I could not use them, as even they required 1" or so of space above them (which I did not have). But I found that they had a flush version that took a larger hole (it's mounted inside a pan sort of like a stove burner pan), and so I was able to enlarge the vent hole "down" and thereby use the original hole and get the P-trap vents in. My concern was water coming in (which is what the traps are meant to stave off). I'm not how they would work for your problem, which seems to be the "reverse."

Here is what Attwood says about them:

The unique design helps to avoid ingestion of water into the fuel tank under normal sea conditions and washdown.
The design includes a series of baffles and traps to allow air to move freely while reducing the possibility of water splashing back into the tank.
Eliminates the need for an anti-siphon loop in the vent hose and allows a more direct routing of the hose to the fuel tank requiring less hose for installation.

What I put in was the Attwood 1674. I think I have a cut-away drawing of it in my album. It works sort of like a Dorade vent. The water (on the way in) basically has to go up and over a baffle to get in. So I guess the fuel would have to do the same to get out, but.... not 100% sure if that would fix your problem (I don't know if that problem happened to most people with the similar vent; I just read about the potential water ingress and decided to do something about it while I had the system apart.)

 

[C-Change]

I just added a pair of Racor LG100 gas/air separators to our 25 cruiser. The things are HUGE but they ranked at the top of the Boat US testing on these type of devices (http://www.boatus.com/foundation/Findin ... nefuel.htm). They were a pain to fit in and they are expensive, but Stacy and I were getting fed up with fuel leaking out the vent during fill ups. We always dread going in to fill the tank and a few fuel docks have given us a hard time when we get the inevitable leak - Usually out of the vent on the opposite side of that being filled. So far have not had a chance to test them out but I'll report on the next fill up.

I am not sure they will fit in a 22 due to their size. Racor also makes a smaller gas only version (LG50). It did not rank as high in the US boat testing but they were testing at high fill rates ( 10gpm and 20 gpm) and they did not slow down when they heard gurgling. They were not too high on the Attwood devices, but Mark installed them on his 25 and they seem to work for him so they may be worth a try since they are MUCH less expensive.

Jan
C-Change

 

[Sunbeam]

Interesting info, Jan. Now I have something to look forward to researching when I get back to "normal" Internet land.

I have not kept up on it, but I believe there is a movement (starting for larger boats) to get boats to a closed system more like automobiles (i.e. not venting gas fumes to atmosphere). I don't believe the requirements (and perhaps usable size) have got down to our size boats yet (for new builds I mean).

Seems like this would have the side effect of not allowing moisture free access to the fuel tanks (through the vent) and/or spilling (out of the vent).

On my 22 it seems to be a toss up on whether fuel will come out the vent or the fill hose itself, with it favoring the fill hose. I only had fuel come out the vent once, and that was my first fill (at a land gas station) and I was merrily pumping away like I didn't expect any problem (ha!). Luckily I had the boat swathed in fuel diapers just in case. But since then (I have slowed down) my only problem has been having fuel come out the fill hose itself, mainly when the tank is getting full and if I went fast enough to cause turbulence where the incoming fuel hit the "fuel surface" in the tank. Angling the fill nozzle back (the same way as the bends in the fill hose) seems to help. Of course preferably, a fill hose would not have any bends. Guess I just need to get saddle tanks such that the fills run straight

Not that I comment to negate the products you mention; on the contrary, I'm interested and will check them out as soon as I can :thup

 

[thataway]

Hmm. Never had the problem--but I don't fill my tanks all of the way full. I suspect that when filling you get some gas into the vent lines? I'll have to check and see how my vents run.

When fueling I watch the tanks, to be sure and leave at least an inch of air visible above the fuel level to the top of the tank...

It is possible that your vents out of the tank are at the outboard edge?