Fuel Overflowing on Winterized Boat

J

Jonah

GreatGrady Captain
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Hi all,

I recently stepped onto my winterized Adventure (covered with a tarp, as in the thread linked below), and smelled gas. Just then, I also heard what sounded like fuel gurgling out of the overflow spout––like it did when I overfilled the tank, the first time I fueled up. I stuck my hand over the edge, and sure enough, gas was coming out of the spout.

I filled the tank one week ago, and didn't notice any overflow at the time. In fact, I worried that I may not have filled it all the way up. Why on earth would it be overflowing now? Was it something about me shaking the boat as I stepped onto it? Surely not––I've stepped on several times in the last week. Is it something about the temperature? It's unusually warm here (70 degrees), and it was closer to 45 or 50 when I filled up last week. I also found that the spare tanks (which I went in there to remove from the deck for winter) were bulging with pressure, given the change in temperature. But why would this cause fuel to spill out, since I thought it was the AIR that expands, and not the fuel itself?

Thanks for any advice! Whatever the cause, it looks like I'm going to have to partially remove my tarp in order to get the gas fumes out and wash down the hull. :-(

Tarp thread: http://www.greatgrady.com/forum/viewtopic.php?f=2&t=23496&start=15
 
Expansion. Liquid expands too. Did you fill it on the way home to your yard? When I fill up before hauling I go for a ride first to use up some fuel. Perhaps try to remove some fuel from your tank otherwise it will keep venting fuel out any time it gets warm until it vents enough out that there is room for the expansion. It really gets warm under the a tarp even on a not so warm day. I would think you will have even warmer days in the spring before you take the tarp off, it will just dump more fuel unless you remove some.
 
Expansion is your answer. Next year, don't fill to the top. I'm a fan of running it down and treating it. Fill it up with fresh fuel in the spring and go. Never had an issue doing it this way since in 20 years. You'll hear people telling you full, empty or in between. I'm usually 1/4 or so full when I treat it.
 
Thanks everyone. Yes, I had been told to fill it up, but hadn't been warned not to get it too full. In fact, I thought the issue was that the air would expand more than the fuel would, and would thereby cause some sort of problem, and so the goal was to get as much fuel (i.e. as little air) in there as possible. But ok, live and learn.

I'm still surprised, since I thought I could go another 5 gallons or so. I suppose I should count my blessings that I happened to step in while it was overflowing, or otherwise I would have been wondering for weeks what was causing the smell. I may siphon a bit out, but given that I can't imagine any more 70 degree days before I take the tarp off for the spring, I may also just monitor it.

So, are there really any 'best' fuel levels for winter storage? I no longer see the advantage of having a full tank, like everyone advised me to do. Instead, it would seem to me that near-empty would be ideal, so that you have less fuel to treat, and can then top up with fresh fuel at the start of the season?
 
I have read all kinds of different suggestions as to how much fuel should be in the tank for winter storage. All good arguments and I have tried full, empty and in between over the years. Now I really don't worry about it. I like and use Fishtales method. Run it down and stabilize. Fill up when launching or if I have a 1/2 tank or so I launch and then run it down then refill with fresh. I like to run out as much of the old as I can before I add new. That said I have an I/O and it has not been fuel or ethanol sensitive. Many OB guys I know do the same thing and have had no issues either YMMV.
 
Jonah said:
Thanks everyone. Yes, I had been told to fill it up, but hadn't been warned not to get it too full. In fact, I thought the issue was that the air would expand more than the fuel would, and would thereby cause some sort of problem, and so the goal was to get as much fuel (i.e. as little air) in there as possible. But ok, live and learn.

I'm still surprised, since I thought I could go another 5 gallons or so. I suppose I should count my blessings that I happened to step in while it was overflowing, or otherwise I would have been wondering for weeks what was causing the smell. I may siphon a bit out, but given that I can't imagine any more 70 degree days before I take the tarp off for the spring, I may also just monitor it.

So, are there really any 'best' fuel levels for winter storage? I no longer see the advantage of having a full tank, like everyone advised me to do. Instead, it would seem to me that near-empty would be ideal, so that you have less fuel to treat, and can then top up with fresh fuel at the start of the season?
Click to expand...

Gas pumper from underground tanks is usually around 55 degrees F. So if your tank temp then heated up to 70 ( keep in mind that if the boat is tarped or wrapped, the internal air temp can go much higher) you owuls have an expansion of about 2 1/2 quarts. Also note that if the fuel nozzle shut off, the fuel tank was probably full to the point where fuel was in the fill hose and most of the vent hose.
I never fill my tank for winter storage. On my 208, I leave 20 to 30 gals of gas ( one solid to one just started flashing bar), add stabilizer, run around the bay a bit to mix in the stabilizer and get it into the motor and that's it. No problem yet in ten seasons.
The second reason for not filling the tank is that should something go wrong, like a water leak or fuel contamination/separation, I will have to dispose of 20 gals of gas instead of 80. proper disposal of gas can be very expensive
 
Check your vent line routing. There might be a dip in it that has allowed gas to settle in there - making it much easier for some to come out the vent. It's possible (although I've never researched this part) that you could be getting gas vapor that is then condensing when it hits the vent screen.

I've always filled my tanks (on various boats for decades). But, in general, I think it's best to either fill it or have it awful close to empty. I treat my gas all the time so I'm not worried about degradation, but condensation is a worry. Especially with aluminum tanks, a partially filled tank will cause more condensation than a full or empty one.

Many of my boats have had vents built into the gas fill, so if any expands it simply drips back into the fill line. On other boats, that have external vents, I've never had any fuel coming out that has been an issue. Some drips, but nothing major. My guess is that you filled the tank much higher than you thought and probably have fuel in your vent line. FYI, fuel will backfill into the vent line faster than the fill line since it's much smaller in diameter. Between the extremely high volume of fuel, the temps, the rocking of the boat (and possibly a dipping fuel vent line)... it was just a good combination of scenarios.
 
Two things come to mind: My 208 has the combo fill/vent filler. I am not sure when that became standard equipment.
Even though the vent line 'connects into the fill line, the cap has a pressure vent on it and the tank is not sealed per se. It has to let in air to avoid a vacuum while gas is being drawn. I suspect that when the tank contents expand, the cap doesn't seal 100% either.
When I cover my 208, the gas cap is under the cover. I always have a gas odor when I open the cover either to check the boat or uncover for the spring. I used to worry about the odor but got used to it. The fumes have to go somewhere and when tarped, they vent into the covered boat.
 
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