Boat Gas and expansion

A question for those Winter fisherman.....

Have you ever had any problems with gas and it expanding with a DRASTIC weather change.

Here is my problem......and it may not be expansion at all.

I went fishing a couple weekends ago........REALLY, REALLY cold. When I got back, I filled the take completely full. Not over flowing, but the tank was full. Today, I smelled gas, and found that I had a small puddle of gas in my garage, When I popped the filler cap, gas squirted me.....

Now, I know from past experience with smaller tanks that gas, when it gets shaken up, will cause the fumes to expand. Is this what is happening.......and if so, what is the answer.......

Mostly though, I simply want to know if other people experience this, etc. BTW.......I've had 5-6 boats, and this is the ONLY one that I've experienced this with, and this boat does not seem to have a "vent valve" like others did.

Any help would be greatly appreciated.

Thanks,

Geo

Geo find that vent! No way should the tank build pressure and spray fuel when you loosen the cap.
Where was the puddle of fuel under the boat located?

Gasoline has to vaporize before it can burn. The vapor Pressure determines how fast the gasoline liquid turns into an vapor. Vapors are oxidized by Oxygen (burned) LEO GER.

The space between the liquid and the inside walls of the gas tank could be called Head Space.

Vapor pressure INCREASES with and INCREASE IN TEMPERATURE. Vapor pressure also may increase with a decrease in Air Pressure surrounding the liquid gasoline. But the main source of increasing or decreasing vapor pressure is due to the air temperatures surrounding the liquid gasoline.

Are you talking about those portable gas tanks used for Boats? I have to squeeze a squeeze ball in the gas tank line to pressurise my gas tank. The pressure inside the tank and the suction coming from the fuel pump on the engine pulls gasoline out of the fuel tank through the fuel lines (hose) and then into the engine.

Might check your fuel lines to see if you have any leaks. Sounds like your system was pressurized ok since it squirted out when you opened the cap. My 6 gal metal gas tank will do that too when I open the cap. Or maybe there is a vaccume inside the tank and air is rushing into the tank. But it does make a whoosing noise as air rushes in or out of the tank as the cap it taken off. That's normal for those small 6 gallon portable gas tanks in boats. My truck's gas cap gives me a whooshing sound when I open it up.

How full are you filling your gas tank in your boat? Might want to leave a little head space. Only put the amount that's stated on the tank. You can add some Stabil or Sea foam to the gas to keep it over the winter. Add the stabit to the gas and then run the gas though the motor for about 5 minutes to make sure that the stabil gets inside the carb and engine good. That will keep the gas from gumming up as the volitale compounds evaporate and leave behind the heavy stuff.

Sounds like mostly a temperature increase, but you may want to find your vent and see if it is plugged since you got a squirt when you opened the fill cap. If it was cold out when you filled the tank, the gas would have been denser and you wouldn't have had as much vapor. Then you put it in the garage, which is likely a bit warmer than outside air temps., and this made the gas produce more vapor which had nowhere to go if your tank has either no vent or a plugged vent. If it does have a vent, then gas should have come out of it when the pressure increased in turn keeping it from spraying you. The whoosh sound you get when opening a fuel cap is usually from a vacuum. If you have a fixed ammount of air and gas in a tank and no vent, then as you run the gas out you actually will pull a slight vacuum on that tank since it has no way of introducing new air to fill the space previously filled with gas. Hope you get it figured out. I don't know too many people that can afford to clean their garage floors with gas at these prices.lol

Hmmm, putting these posts together, this is my guess. You filled the tank in cold weather, it warmed and expanded, going out the vent onto your garage floor until something floating in the gas plugged the vent, causing it to spit at you.

Pay attention to your gas gauge in your vehicle when it is cold and after it worms up.
DAVID

I've never tried putting WORMS in my gas. Does it keep them warm?lol.

If your boat is sitting for any amount of time you might want to drain the tank as most outboard makers are suggesting you do instead of keeping it full like they used to tell us..... now because of ethanol in the gas the alcohol can seperate causing engine damage, the FAA has banned regular gas also for the same problem in small prop planes that used to use reg. gas. Its called phase seperation

Why don't you run it for 10 minutes in your drive way using a flusher and burn off a little of the gas.