Fuel caps leaking

[Pighunter]

I fueled up 228 last Thursday for the first time. I filled both tanks, as soon as the pump clicked off I stopped. I didn't top off. That night about 10 pm I smelled gas I went out and had gas leaking from the front cap I tightened it as tight as I could and wiped it off but there was yellow streaks running down the side of the boat and I pulled the trailer wheels on blocks to try and get gas to run away from the caps. Yesterday morning I buffed out the yellow streaks and checked out my gaskets, they look fine but I'll order a new set. This morning it was leaking again so I siphend out about 1/2 gallon, it's all in the hose. Now I just went out and gas is coming out of the main cap I took out a gallon. It's hot today 104. Anyway is it normal for the tanks to be so full that the gas can't expand without leaking?

 

[Bloodweiser]

Check your vent ?

 

[Bloodweiser]

Gas does expand some with temperature

 

[Pighunter]

Gas does expand some with temperature

I understand that but It just seems like they shouldn't be full up to the cap? And the vent must not be working, I'll take a look later when it's bearable outside.

 

[Halfhitch]

If the fill hose is in the aft portion of the tank and you don't have a vent in the forward portion of the tank, then if the tank is full and the bow is higher than the stern then there is likely a bubble of trapped air that expands alot with an elevating temperature change and forces the gas up the fill hose. It doesn't mean the seal on the cap is bad. If you have the vent integrated into the fill cap like I do then air expansion will force gas up the vent hose and out the intended air vent. The solution is to install a vent in the forward portion of the tank which is a lot of work. Easiest solution is if you need to fill as full as possible for an extended trip then park the boat with the stern high. (if you have an aft fill hose),Even if you have to unhitch and lower the tongue jack.

 

[Pighunter]

If the fill hose is in the aft portion of the tank and you don't have a vent in the forward portion of the tank, then if the tank is full and the bow is higher than the stern then there is likely a bubble of trapped air that expands alot with an elevating temperature change and forces the gas up the fill hose. It doesn't mean the seal on the cap is bad. If you have the vent integrated into the fill cap like I do then air expansion will force gas up the vent hose and out the intended air vent. The solution is to install a vent in the forward portion of the tank which is a lot of work. Easiest solution is if you need to fill as full as possible for an extended trip then park the boat with the stern high. (if you have an aft fill hose),Even if you have to unhitch and lower the tongue jack.

Great information, and yes the bow is much higher then the stern. Just the way it came off off my truck and I didn't think about lowering but I'm going out and doing it now.
Thanks

 

[SkunkBoat]

I assume its a vented cap? Otherwise, that is strange.
I had same problem on an older boat with separate vent. Filled the tank on the trailer in November 38 degrees and parked it for the winter. 85 degree day in April, gas coming out the vent
The vent line is much smaller diameter than the fill hose so the gas was able to reach the vent. I'm guessing its coming out the vented cap. It would take a lot of gas to fill up the fill hose.

Also, if your vent and fill tank fittings were covered with gas due to the tilt of the boat, its basically not vented.

 

[Pighunter]

I lowered the bow at least 10" and I thought it was stopped. Twenty minutes later I went out to take these pictures of the caps. While taking the picture they began oozing out. I pumped out both fill hoses with a 28" hose.

Pictures are in reverse order and I tried to add more but it said file to large.

 

[Bloodweiser]

man that sucks. We have had such a huge jump in temp in our area it’s crazy .

 

[Pighunter]

man that sucks. We have had such a huge jump in temp in our area it’s crazy .

Yeah it really does suck! Like I said it was my first time filling it took 74 gallons between the two. I was trying not to over fill , slowly and as soon as it clicked I stopped.

I just went out and raised the bow 5"?? I'm hoping there is a sweet spot?

What's the surge plug for on the caps? Where is it supposed to vent?

 

[wrxhoon]

I think you will find both filler and vent hose to be to the front of the tank. I notice you have 2 tanks , I don't know if the front ( small) tank is the same . Lift the floor plates off to check . In this case you have to lift the front as high as possible.
Like you said it is very hot now and the gas will expend and vents out.
One way to sort it out use the boat, burn the fuel.

 

[Blaugrana]

I think you will find both filler and vent hose to be to the front of the tank. I notice you have 2 tanks , I don't know if the front ( small) tank is the same . Lift the floor plates off to check . In this case you have to lift the front as high as possible.
Like you said it is very hot now and the gas will expend and vents out.
One way to sort it out use the boat, burn the fuel.

Agree with the above. There was an older post here that mentioned the fuel cap leaking after filling up when the tank was filled/ overfilled.

Since reading that, if either of my tanks overflowed at the pump or came close to it, I run on that tank for a good 5-10 mins at speed. More preventative and not sure I would have the same issue with the cap leaking if I didn’t....

 

[seasick]

I think it is just plane expansion.If the fuel level is high enough, it will vent out of the cap assuming a dual purpose type of cap ( if hull vented, it will exit there). The expansion rate for gasoline is more than you would expect.
The fact that the vent hose is smaller than the fill makes no difference for a combo fill fixture. If gas flows up the vent line, it will drain back into the tank as long as there is room which obviously there isn't.
My advice is to fill up on the way out for a trip and not right before your dock. That way, you will burn off some gas and lower the level in the tank.

The calculations for the actual expansion are complicated since the tank also expands when it gets warmer but general estimate for gas is an expansion of .00053 per degree F of change.
Gasoline underground is about 55 degrees F but that can vary depending on when the last load was delivered and what its temperature was.
Let's assume that the gas sat underground long enough to stabilize in temp. The next day you fill up your 120 gallon tank.Over time, the gas warms up and it's a hot day so assume the temp rises 30 degrees F
The expansion is .00052 x 120 x 30 or 1.9 gallons! Assuming you filled your tank till the nozzle clicked, the fill hose if pretty much full. Where does that 1.9 gallons go? Out the vent!

 

[DennisG01]

This is really, really simple... you put too much gas in the tank. Filling till the nozzle "clicks" off is wrong - especially going slow, as you said. In essence, you filled the tank and then continued to pump gas in and filled both the fill line and the vent line (your vent fitting is just inside the fill deck plate).

Boat fuel tanks are different than a car. Proper fill up procedure... listen as you fill up. When you hear the "gurgle", stop.

FYI... even "topping off" a car's tank has the possibility to saturate the carbon filter and cause issues. Not sure what year your boat is - but somewhere around 7-10 years ago carbon canister/filters started to be used in boats, too. If you have one, it's probably done for.

 

[leeccoll]

I'll agree too that it's a matter of too much fuel.

I filled up my single tank once as you did, and excess gas was dripping down the side of my hull from my vent.

I try to listen as it is filling and nearly full, and then stop conservatively, so maybe I am 90-95% full.

Good enough for me~

 

[Pighunter]

Yeah it will be good enough foe me also. I've owned more boats then I can remember and this is a first for me.

 

[ScottyCee]

Been there, done that. I had too much fuel in mine prior to launch this year as well. Makes a mess, had to pump some out.