Gas tank vent overflows at 3/4 full.

[joetann]

I have a 104 gallon tank on my boat and can only get it to accept about 65 gallons before fuel comes shooting out the vent. I've tried to slow down the delivery of fuel with no luck. Any ideas on why this is happening?

 

[Almeja]

Re: Gas tank vent overflows at 3/4 full.

I have the same problem on a smaller scale in my 19' bowrider.

Since I'm at the back of the boat filling, the boat is usually sitting stern-down at the gas dock and an air pocket forms in the uphill end of the gas tank.

Getting the bow down by moving all available passengers to the front helps quite a bit in my boat. Without moving passengers, I can only get the tank about 3/4 full.

Your situation my be different, but I suspect re-engineering/relocating the vent/fuel filler/tank is probably the only real answer.

Chalk it up to poor design.

 

[tashasdaddy]

Re: Gas tank vent overflows at 3/4 full.

Almeja, the problem i see with your technique is when the passengers move back to the rear , you are pouring gas out the vent. the solution is see is to loop the vent hose higher than the vent opening.

 

[Almeja]

Re: Gas tank vent overflows at 3/4 full.

"... when the passengers move back to the rear , you are pouring gas out the vent."

Fortunately, the vent opening and filler have enough elevation relative to the tank so that doesn't happen.

The design problem was that the builder put both the vent and tank fill on the aft end of the tank... which is the lowest part in a 'normal' attitude. Cheaper to build and easy to access the connections... but not very functional when it comes to filling. :>(

It is one of several 'features' on my boat that represent victories of form over function.

 

[steelespike]

Re: Gas tank vent overflows at 3/4 full.

Just wondering how empty is the tank when you attempt to fill it.My expierence with small boat tank gauges is not too accurate.if the gauge reads empty and is off only an 1/8 of a tank that could be 13 gallons and most tanks still have say 2 to 5 gallons remaining at empty there could be 20 gallons left in there at empty if things are a just a little off.Have you ever run it dry or tried to syphon the remaining gas at empty.If the tank isn't perfectly level at rest you could have a big pocket of gas in there. and the gauge could be way off.

 

[Solittle]

Re: Gas tank vent overflows at 3/4 full.

My bet is on a bad sending unit for the fuel gage. They are easy to replace. Happened to me a couple of years ago.

 

[BrianS.]

Re: Gas tank vent overflows at 3/4 full.

Are you visually seeing 65 gallons in the tank or are you going off the guage?

 

[cart7]

Re: Gas tank vent overflows at 3/4 full.

Your problem is with existing gas already in the vent hose. As the tank fills you start pushing the existing gas in the vent line out the hose. If you can get to it you can try tilting the vent hose up and allowing the fuel to run back into the tank.

 

[calwldlif]

Re: Gas tank vent overflows at 3/4 full.

Common thing
Fill slower
drop trailer to ground
Given the tank isn't really full

 

[joetann]

Re: Gas tank vent overflows at 3/4 full.

Are you visually seeing 65 gallons in the tank or are you going off the guage?

Brian,
I measure the gas in the tank with a small tape measure. 1" equals 6 gallons. 17" total depth. The sender or the guage is not accurate and I'm waiting for my repairman to look at that.

The vent comes out of the top of the tank and makes an abrupt 90 degree angle, then the hose proceeds to the vent which is about 10 or 12 inches above. I'll have to look again, but I don't think there is any play in the hose to the vent. Pretty much straight to the vent fitting.

 

[hiflyer]

Re: Gas tank vent overflows at 3/4 full.

You might try pulling the fitting out of the tank and see how deep it goes in to the tank. I am proabably wrong but you just may, have a tube ect in the tank by mistake, on the end of the fitting that will push gas out when covered with gas.
The vent should be as close as possiable to the top of the tank and at the higest point. Also, you might try putting in another one at the high point.