Self vented gas tank. Are they water proof ?

[pecheux]

To make a short story long ... lol I had a universal plastic gas tank hooked up on my 6 hp OMC and the boat-motor-tank remained out on the lake all summer unprotected from rain and sun.

A few weeks ago the engine stalled regulary and it looked like the primer pump was not pumping any gas to the motor. I then installed a genuine OMC tank that has NO air vent screw and problem was solved. At that time I did not know what the problem was. Ended up the small hole in the vent screw was blocked ... dont know what did it but I suspect the venting drew moisture and pollen or dust.

I also suspected that water could get in the tank via that small hole in the vent screw on a rainy day.

I beleve the venting on the original OMC tank is done via under the cap therefore I tend to beleve water could not infiltrate the tank when it rains.

Question is: am I right or wrong about venting and water infiltration on either tank ?

Thank you and y'awl have a great day.

 

[JimS123]

Re: Self vented gas tank. Are they water proof ?

Your analysis sounds right to me. Personally, I have little use for the newer plastic tanks. The only issue I have ever had with an old OMC tank was that the gauge failed because the float's coating was dissolved by ethanol. Simple fix though. The fill pipe and cap have a lip, so I don't see how water could ever get in the tank unless it was submerged, and even then it would float, though maybe it might capsize.

 

[Home Cookin']

Re: Self vented gas tank. Are they water proof ?

If you leave your tanks out when moored, put a baggie, loosely, over the cap if it's the kind with a vent screw.
A driving rain might force water up under an OMC type cap, but it couldn't be that much (or that much coming in a vent screw).
Due to ethanol issues it's better not to leave your tanks out in the sun if you're not using them.

 

[LORDY611]

Re: Self vented gas tank. Are they water proof ?

Due to ethanol issues it's better not to leave your tanks out in the sun if you're not using them.

Please elaborate. What does leaving the tank in the sun have to do with ethanol in the gas? And does it matter if the tank is plastic or steel?

 

[dingbat]

Re: Self vented gas tank. Are they water proof ?

Please elaborate. What does leaving the tank in the sun have to do with ethanol in the gas? And does it matter if the tank is plastic or steel?

The amount of water E-10 will hold in solution phase separation begins is a function the temperature of the fuel. The higher the temperature the more water it will hold in suspension.

The problem comes when the heated fuel is cooled. Cooling the fuel lowers the amount of moisture it can absorb and the excess is then shed in the form of phase separation. Not to mention that heating the fuel raises the rates of the evaporation

 

[LORDY611]

Re: Self vented gas tank. Are they water proof ?

The amount of water E-10 will hold in solution phase separation begins is a function the temperature of the fuel. The higher the temperature the more water it will hold in suspension.

The problem comes when the heated fuel is cooled. Cooling the fuel lowers the amount of moisture it can absorb and the excess is then shed in the form of phase separation. Not to mention that heating the fuel raises the rates of the evaporation

so the water gets into the E10 gas as humidity, and held there more as the heat increases? Then, as the tank and fuel cools, the humidity comes out of solution and becomes a layer of water in the tank?

So, what happens in the case of my steel OMC tank without an air vent (I presume this because when it sits in the sun and I open the tank, the gas is heard escaping under pressure)? Because it is not subjected to the atmosphere except when refueling, little humidity gets in?
And, would it be correct that plastic heats up less than steel?