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Hi
I have a '92 Sundowner 205 and am experiencing a confusing (to me) situation.
I have a 44 gallon aluminum under floor gas tank that is venting liquid gas out of, yeah you guessed it, the VENT. This only happens when the sun is beating directly down onto the floor of the boat.
The tank is NOT filled to the top by any means, but it probably has at least 40 gallons in it.
I know the vent is clear all the way to the tank, because when I blow into the vent's external drain hose, hard enough, I can hear the tank "pop" as it expands slightly, and the pressure comes right back out of the vent hose when I stop blowing.
What is weird is that I feel a fair amount of pressure when I unscrew the main gas cap. How is it possible for there to be a buildup of pressure with a clear vent line????
Any comments would be much appreciated.
Thanks
Bernd
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Seems to me that there is only one answer to the question. Pressure can only build up when there is no vent. If there were an open vent, pressure simply wouldn't build up.

It has to be that your vent is being blocked some how. Maybe when you blow on it, you are also blowing whatever is blocking it temporarily out of the way.

Kinked hose? Insect nest or other material blocking it?

_________________
-Bill Kearney, 2005 348 Vista

Ok - this is a pretty serios issue. First, a restricted vent tube will not give the liquid fuel flow out as you have described. The vent allows vapor to escape while fueling, allows for fuel to be taken by the engine without collapsing the tank, and allow the tank vapor pressure to exchange while the tank temperature is changing. What I hear is that the liquid fuel is covering the tank vent tube. This can be from an overfill condistion or the angle of the tank as related to wherethe vent is located. If the vent tube is aft, and the boat is stored at a steep angle, then what you described will occur. If the vent tube is forward on the tank, then what you described should not occur. Take a look at the tank vent tube location and how th boat is being stored. The problem may be as simple as not setting the storage angle as steep. Hope ths helps a bit.