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Is this a sure way of telling if your tank is full?

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Is this a sure way of telling if your tank is full?

Old 01-27-2019, 05:55 PM
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Default Is this a sure way of telling if your tank is full?

If it spits fuel out the vent and then you get like 3 more gallons in and it spits out the fuel fill, does that mean the tank is full? I've had it had it spill out the fuel fill and never out the vent line. I'm thinking I have some kind of restriction, but for the time being if it shoots put the vent first does that mean it's actually full?
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Old 01-27-2019, 06:26 PM
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If it shoots out the vent and you force in 3 more gallons...........it means you are riding around on a IED!!!
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Old 01-27-2019, 06:35 PM
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Probably, unless you have a blockage somewhere. I prefer to make sure the amount of fuel I add when it seems topped off also matches the amount my MFD shows that I burned.
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Old 01-27-2019, 06:40 PM
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Originally Posted by Grunts N Grits View Post
If it shoots out the vent and you force in 3 more gallons...........it means you are riding around on a IED!!!
Bullshit. I've done it that way for years on my other boat.
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Old 01-27-2019, 06:51 PM
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Originally Posted by fishmaster273 View Post
Bullshit. I've done it that way for years on my other boat.
If you know then why are you asking?
When it spits out the vent it's full. After that you're just filling the fuel fill hose, which isn't too smart.
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Old 01-27-2019, 07:02 PM
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If it's coming out the vent and fill, you may have to burp the tank. Just rub or pat its back. Remember the burp rag to wipe the occasional mess.
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Old 01-27-2019, 07:07 PM
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Check with a match!! Actually to check the vent, with the cap off, blow gently into the vent. You should hear air in rhe fill pipe.
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Old 01-27-2019, 07:22 PM
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How old is the boat? Newer rigs have a charcoal filter on the vent line. Fuel should not get in or through it
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Old 01-27-2019, 08:14 PM
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Originally Posted by v12mac View Post
How old is the boat? Newer rigs have a charcoal filter on the vent line. Fuel should not get in or through it

Zzzactly right. ! How old?

If it is a newer boat with one of the screwy more-recently mandated restricted-emissions fuel systems with partially pressurized tank , charcoal cannister and no-longer-open-venting, if you pump add'l gas in after the pump 1st clicks off from back pressure you will fill the charcoal cannister and it may no longer vent at all until you disassemble the cannister unit and replace the soaked element. Similar with cars for a long time now although they tend to be more forgiving in that respect.

But whether it is a new or old system, you could have a vent line which now has a fuel or water trap sag in it either from terrible original routing under sole supports or from fatigued and broken vent hose hangers. ...Or have a partially restricted vent fitting screen .
If fuel or water is sitting in a dip in that hose , venting air cannot easily pass though it in or out. The greater the amount of trapped liquid , the harder for air to vent and more fthe fuel will tend to back up at the deck fill before tank is full. Obviously , in-tank air must be displaced/vented out at sufficient rate for fuel to enter at full pump speed. That said. sometimes filling at slower nozzle flow rate , moving the nozzle so it slides farther into the deck fill, or swinging the nozzle handle to one side or the othermto change flow angle can help facilitate smoother continuous flow.
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Old 01-27-2019, 08:24 PM
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They have it looped so it's either going to go back into the tank or out the vent, nothing is going to get stuck in the line. Now unless their is a sag at the bottom portion of the hose where it's between the deck and the gas tank I don't know cause I can't really see that part. If their is a sag is that where it's going to be? On the tank side? btw it's an old boat, so no epa bs.
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Old 01-27-2019, 08:26 PM
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Originally Posted by Still Stoked View Post
Check with a match!! Actually to check the vent, with the cap off, blow gently into the vent. You should hear air in rhe fill pipe.
You can see fumes coming out the vent when filling. Although compared to my other boat I recall seeing more and actually hearing the air come out the vent so maybe their is a clog.
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Old 01-27-2019, 08:27 PM
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Originally Posted by fishmaster273 View Post
Bullshit. I've done it that way for years on my other boat.


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Old 01-27-2019, 09:18 PM
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Originally Posted by fishmaster273 View Post
They have it looped so it's either going to go back into the tank or out the vent, nothing is going to get stuck in the line. Now unless their is a sag at the bottom portion of the hose where it's between the deck and the gas tank I don't know cause I can't really see that part. If their is a sag is that where it's going to be? On the tank side? btw it's an old boat, so no epa bs.

Yes , if there is a part of the vent hose you can't see, that is surely where it's going to sag.

Could you inspect that area with a flashlight and mirror , or inspection cam?

Even if there is a slightly-low length of the vent hose which holds fuel from an over- topped-off tank fill but the dip is not low enough that the liquid cuts off all free-air-flow , the level of the retained liquid in that hose can still reduce the effective free-air-passage upper area of that section to a small fraction of that of the higher sections of the hose.

That effect in a typical 5/8 " ID gas tank vent hose might be equivalent to having ,say, a 1/4" ID hose instead. So air cannot get out of the way of the incoming fuel at the same rate. But you could still see fumes exiting the hull vent and possibly not hear gurgling you might otherwise hear if a cross section of any part of the vent hose was fully liquid-filled.
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Old 01-27-2019, 09:19 PM
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I don't let it overflow out of the fill tube. Usually the issue is it clicks off at the fill tube first and never spits out the vent tube.
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Old 01-27-2019, 09:22 PM
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There is an inspection plate for the hoses. Good idea on the mirror. I'll try that. I'd rather not stick a flash light in the hole that's a little too risky imo. You always have to be careful with gasoline. Are you saying that the fuel could stay in the sag all the time? even until the next time you fill up?
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Old 01-27-2019, 09:27 PM
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Originally Posted by fishmaster273 View Post
I don't let it overflow out of the fill tube. Usually the issue is it clicks off at the fill tube first and never spits out the vent tube.
That could be the result of a high reverse-trap loop inside at the hull vent. If the highest point is near to the deck fill the vent may not spit 1st.

Plus, if the tank's vent outlet is higher than tank fill hose fitting, the fuel can back up to the nozzle before the tank vent outlet has fuel entering it. or at least before fuel reaches the top of the vent loop.
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Old 01-27-2019, 09:37 PM
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It spit first out the vent the last time I filled it up, but that time I made sure the pump was on a slower setting and stopped a couple times in between filling.
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Old 01-27-2019, 10:28 PM
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If your vent is not clogged you should hear it whistling as you add gas. When that whistling starts to increase in frequency, slow down. when a drop of fuel spurts out, stop. After some practice, you'll be able to stop just before fuel spurts out.
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Old 01-28-2019, 04:25 AM
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I have filled fuel tanks on various boats over the years and I have never had to let gas overflow to get a full tank. I would reassess your strategy...
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Old 01-28-2019, 05:07 AM
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Originally Posted by fishmaster273 View Post
There is an inspection plate for the hoses. Good idea on the mirror. I'll try that. I'd rather not stick a flash light in the hole that's a little too risky imo. You always have to be careful with gasoline. Are you saying that the fuel could stay in the sag all the time? even until the next time you fill up?
Lol
You always have to be careful with gasoline. Says the guy overfilling his tank and splashing fuel everywhere.

I'm sure this is a spoof post but Its early and I'm a little slow so I'll play along.
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Last edited by 1976K204x4; 01-28-2019 at 05:13 AM.
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