Gas overflow valve/smell of gas

[pcbayou]

I'm trying to find the source for a gas smell in my boat, and I'm wondering if there's a problem with the gas overflow vent that connects to the tank.

The last two times I filled up, gas spurted out the vent immediately when I started pumping. The second time, when I filled up yesterday, gas didn't spurt out when the tank was full as it usually does -- the pump just automatically cut off.

After the first time I had the gas spurt, I noticed a fairly strong gas smell when I opened one of the boat's hatches. But eventually it went away. Today, when I opened the battery hatch, I caught a faint whiff of gas again.

My dealer's mechanics haven't found any leaking hoses or connections. Should I ask them to check the overflow vent?

By the way, thanks to all the troubleshooters who answered my other post about battery problems. It's always something.

[Ifishtoo]

How are your lungs? LOL

Also, does the sunlight hit the deck of boat? That "heat" will create some pressure inside of a tank of fuel? Regardless, it should vent gasoline vapors and/or gasoline outside, through the vent line........... NOT INTO THE BILGE.

Open up all the hatches and leave them open. By the way, when the bow is elevated, is there any gasoline to be seen in the bilge, at the stern (where water collects)?

Once you have "aired out the hull" and with a full tank, open the fill cap. Place a rag or something soft around it. Take a big breath and blow into the fill. If you have other means to force some air into the tank (small compressor) place ONLY 5-7 psi (no more than that!!) into the fill cap. A sponge can also help seal off the fill cap . Fuel tanks are tested/rated to with stand 5-8 lbs......NEVER EXCEED 7 PSI. A strong set of lungs will generate 3-4 psi.

When you force ANY air into that full tank, someone else should be waiting/watching/sniffing at the vent, outside of the hull.

If your rig is over 7yrs old, it could be: 1) the vent line is leaking fuel, 2) the fuel line to engine is leaking fuel, 3) or a leak in/at the tank. Perhaps a critter (mud dobber) has stopped up your vent line. Rubber fill, fuel, & vent hoses over 6yrs old were NOT made to tolerate ethanol. The ethanol deteriorates them. As time passes, if you have a leak, regardless of where it is, you will notice the odor increasing, and eventually you may "see" some fuel in your bilge. If you would like some help, I'm retired, not too far away, and, according to my wife, have owned way too many boats.

Good luck.

[pcbayou]

Thanks, Ifish. Neither I nor the dealer has found any sign of a leak. Maybe I'll try replacing the vent line to see if that takes care of it. From what you've said, it sounds like I'll need to do that anyway.

I'll try the blow test, too. I never even knew lungs had a PSI rating. The things you learn on this forum!

[SS-342]

When do you fill up? Before fishing or after fishing? I started out filling up after fishing and ran into this same problem due to expansion of gas. Switched to filling up on the way fishing and solved problem.

Whatever, it needs to be found and fixed. Fires aboard ship is a terrible thing!

Something like a fire in a gun powder warehouse or fireworks store.

[pcbayou]

I started out filling up after fishing and ran into this same problem due to expansion of gas. Switched to filling up on the way fishing and solved problem.

I usually fill up at the beginning of the trip. But I usually keep a pretty full tank -- rarely less than half-full. So maybe the gas is expanding and building pressure while the boat is idle -- something to consider, I guess.

Thanks for the feedback. You're certainly right about needing to find and fix it.

[SS-342]

If your vent cap is open there should not be any pressure build up. Mine over flowed out the vent when full.

[Slough]

If your vent cap is open there should not be any pressure build up. Mine over flowed out the vent when full.

[pcbayou]

Thanks -- sounds like I need to check out that vent.

[Ifishtoo]

Direct sun light can be a "big" deal when it comes to expansion issues. Years ago, I had a boat with a very large fuel tank. If it was topped off, then sat in the sun, fuel would almost always drip out of the vent line.

[MudDucker]

If you have ever put ethanol in your tank and you have an aluminum tank, you might have pin hole leaks. I have found out from BAD experience that the combination of ethanol gas and saltwater creates a super corrosive that will eat up aluminum. I am in the process of trying to find someone to remove my tank out of my old Pro now, instead of fishing.

[pcbayou]

Ouch! Spring is no time to be making that kind of boat repair. I'm not sure whether my tank is aluminum or maybe plastic/PVC? The mechanics did say cutting out the tank was an option, but we haven't gone there yet. Let us know how it goes. I may need that service, too.

[silverking]

If you have ever put ethanol in your tank and you have an aluminum tank, you might have pin hole leaks. I have found out from BAD experience that the combination of ethanol gas and saltwater creates a super corrosive that will eat up aluminum. I am in the process of trying to find someone to remove my tank out of my old Pro now, instead of fishing.

If you haven't found someone in Valdosta MD, Mike's Marine Ways in St. Marks is well-versed in this predicament and has repaired several forum member's boats. He's located just off Hwy 98 and Woodville Hwy, behind the Dollar General store.

[MudDucker]

If you have ever put ethanol in your tank and you have an aluminum tank, you might have pin hole leaks. I have found out from BAD experience that the combination of ethanol gas and saltwater creates a super corrosive that will eat up aluminum. I am in the process of trying to find someone to remove my tank out of my old Pro now, instead of fishing.

If you haven't found someone in Valdosta MD, Mike's Marine Ways in St. Marks is well-versed in this predicament and has repaired several forum member's boats. He's located just off Hwy 98 and Woodville Hwy, behind the Dollar General store.

Thanks, I had a man come look at it last week, but haven't heard his estimate yet. If he can't get it done, I will check with Mike's.

[flogator]

Posted on this forum - problem with gas in bilge - the problem was the sending unit (top of built-in gas tank) was bad. gas expanding would spill into bilge technician said the sending unit should be replaced/checked every 4 -5 years. Mine was completely rusted away

[SS-342]

Glad you found the problem and got it fixed. Thanks for letting us know!