Diesel Fueling Vent Frustrations - Pun Intended

B

BOSCBIJI

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Aug 11, 2025
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Fluid Motion Model
Ranger Tugs Models
Howdy folks -

Curious to hear from Diesel boat owners, particularly recent model 29's and 31's...I CANNOT seem to fill my tank without fuel coming through the vent. Its not a lot, but its near as I can tell impossible to avoid.

Happens with the pump running slow, running fast, running slow then fast, running fast then slow. Happens at the beginning of fueling, midway and at the end. Cold weather, hot weather, no additive, additive...nothing seems to make a difference.

Maybe we have a vent line problem from the factory? We have no other fuel issues and the vent seems to otherwise function correctly.

Doesn't seem like anything I can do keeps the fuel from gurgling at least a dribble out the vent. Which while manageable, its getting pretty old holding an absorbent pad under the vent while I try to pump at the same time.

Thanks in advance!
 
I have a 2017 R29 sedan and have experienced the same situation when fueling. I found that positioning the fuel nozzle certain ways and speed of delivery helps but does not eliminate some fuel coming out the vent. I can’t give you specifics as it varies with the fuel nozzles used.

Mike
 
Ours only happens at the end of the fill.
 
This issue has literally been discussed for at least a decade. There are several commercial devices to address the issue.
1. Inline Vent Line Surge Protectors like the Attwood Fuel Vent Line Surge Protector.
2. Fuel whistle alarms like the Scully Vent Pipe Fill Signal or the Green Marine Fuel Whistle for smaller marine hoses.
3. Deck-Fill Overfill Preventers which are portable or retrofittable devices that plug directly into the deck fill pipe.
4. Just don’t fill your tank to full. We fill ours to 90%. Only once in every 4-5 fills to we go past 90% and then we use a whistle alarm. The fuel level read out at the Garmin is pretty accurate for fills between that.
 
I took my fuel float out of tank to check it. There is two inches of air space left when float is maxed out. I have no idea how many gallons are in the 145 gallon tank when Garmin reads 100%. I was told by a Ranger Tug whiz that I should fill past 100% and stop when I hear the magic gurgle. Forget all that. The game changed when I got a "fuel catch" brand bottle. Or another brand is "no-spill". $45 on Amazon, and sometimes half that on eBay. I read how many gallons are left on Garmin, subtract that from 145 gal. Pump fast until near that and slow down until a little fuel flows into bottle. Bottle fits vent with two function cups. Add run-away string to bottle unless you want to pay another $45. Most expensive plastic bottle around yet worth it.
 
I fill to 15L underfill or "magic gurgle", whichever comes first. Occasionally I get inexplicable fuel mist coming out of the vent before approaching full; unusually foamy fuel for some reason? (Collapsing foam known to generate aerosolized mists).
/diatom
 
There are two fuel tanks on the R43, the aft one spits out quite a bit from the vent but the forward tank dribbles not at all. I think the forward tank has a longer distance from the tank to the vent and that might be the reason. Anyway, as Mastercraft mentioned, using a vent minder is what I do also. The suction cups stick better if you wet them first and also rub the salt off the hull before attaching.

1779716026913.png


In addition, I use this device that is designed to capture overflow, but in fact we never get to that point. The real advantage of this is that it amplifies the sound of the fluid in the pipe and I find it much easier to detect the change in pitch when I get to the full tank level.

1779716245181.png
 
I was at the fuel dock the other day...put in 80 gallons of diesel fuel. Of course, I got a dribble from the vent occasionally and I was concerned about it until the fuel attendant says "We don't worry about it unless it's 20 gallons or so." 😀
 
scross said:
This issue has literally been discussed for at least a decade. There are several commercial devices to address the issue.
1. Inline Vent Line Surge Protectors like the Attwood Fuel Vent Line Surge Protector.
2. Fuel whistle alarms like the Scully Vent Pipe Fill Signal or the Green Marine Fuel Whistle for smaller marine hoses.
3. Deck-Fill Overfill Preventers which are portable or retrofittable devices that plug directly into the deck fill pipe.
4. Just don’t fill your tank to full. We fill ours to 90%. Only once in every 4-5 fills to we go past 90% and then we use a whistle alarm. The fuel level read out at the Garmin is pretty accurate for fills between that.
Click to expand...
It’s not a full tank issue.

Fuel vents at any and every point in fueling from low, mid, high. In fact if anything, there seems to less fuel venting in the final 30 gallons.

We leave a 5 gallon buffer so as not to overflow the vent or top.

Seems like the capture devices make the most sense.
 
My observation: High-speed fueling systems tend to push a lot more fuel out of the vent.

For example, every time I’ve refueled at Foss Harbor Marina (I added 40 gallons yesterday), I get a decent amount of fuel coming out the vent. It doesn't matter how full my tank is. It happened at 25%, 50%, or 75%. Same thing happened at Morrison Fuel dock on Lake Union.

When I am refueling with slower pumps, I usually see about a teaspoon of fuel come out of the vent.

I’m pretty paranoid about fuel spills. I have the two devices mentioned in the thread and I use them every time I am adding fuel.
 
I installed the vent surge protector on myR29 and never had another issue.
 
On my 2022 C30 I found the factory had neglected putting a sufficient loop in the vent hose. I discovered this during one of my early fills of the diesel tank. Fuel suddenly poured out the vent! I rectified this and have had no problem since. I encourage folks to double check the vent hose. Even if a loop had initially been made, depending on the nature of the loop and/or the surrounding space, it may begin to flatten out.
 
I installed the racor lg100. Easy process on my boat (other than the standard twisting the body, scraping the arms)
 
RobMcClain said:
On my 2022 C30 I found the factory had neglected putting a sufficient loop in the vent hose. I discovered this during one of my early fills of the diesel tank. Fuel suddenly poured out the vent! I rectified this and have had no problem since. I encourage folks to double check the vent hose. Even if a loop had initially been made, depending on the nature of the loop and/or the surrounding space, it may begin to flatten out.
Click to expand...

Do you have any picture of the "right" loop that could help me to inspect my boat? I just accepted the fact the fuel leaks through the vent and I have the Fuel Catch device to catch the spills, but never tried to fix the root cause.

Thank you

Alex
 
Sorry Alex, I didn’t take a photo of it. The line essentially routed out the hull with little rise and no meaningful loop, so the fuel had a clear exit path. As a result, the fuel didn’t dribble out but rather shot out. I always listen very closely as I fill the tank to prevent any spill, and there was no warning whatsoever. The owner of the fuel dock instantly suggested there was no loop, and he was right. As I fixed the hose I also installed an H2Out fuel guard which allowed me more hose for making a satisfactory loop.

Fuel Guards | H2 Out | H2 Out

h2out.com h2out.com
 
In looking at the RT documentation online, it's not clear to me where the loop would reside...or how to get access to creating it. I'd assume the loop goes nearer the fuel port rather than the tank, but not clear where...
 
My loop occurs just before the hose attaches to the vent fitting in the hull.
 
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