fuel line vent cutoff valve to diminish ethanol separation

[Timeking]

As you know, the ethanol in the gas (in Florida) absorbs moisture from the air. When it gets to a critical level, it separates to the bottom of the tank. When you start your engine (it will start), the separated ethanol displaces the lubrication oil from the moving parts ... and the engine blows up. Yay!!! Since the daytime and nighttime temperatures are different, the below decks tank will "breathe", suck a little air in when its cold, blow a little out when it warms up. Each time it does this, a little more moisture goes into the tank. I am PLANNING putting a gate valve in my tank vent line to prevent this. I know that if I forget to open this valve when I fuel up I will have a mess, and/or if I run the engine I will wind up crushing the 67 gallon fuel tank from atmospheric differential, maybe causing a leak, and the whole boat blows up. Again, Yay!!! So ... obviously ... it will be important for me to open up this valve when I am using the boat, and closing the valve when it sits in the yard.

Any thoughts on my scheme?

PS: there is no station located near me that sells non-ethanol contaminated fuel. Bummer.

 

[GA_Boater]

What are your plans when the tank blows up from over expansion caused by the Florida heat? That's a bigger concern that crushing the tank by forgetting to open the vent and running the motor. What kind of super-duper fuel pump does your motor have that can suck fuel out of an unvented tank to the point of collapsing the tank. I'm not sure the motor will run long enough to suck the tank into a crumpled mass before dying of fuel starvation.

Have you actually experienced this separation? When you are out running the boat and all this moisture laden air is drawn in through the vent, how long before you are sucking water into the motor?

Thoughts on your scheme? You asked- Forget about it. IMHO

 

[JASinIL2006]

If it is that big of a problem, wouldn't the easiest solution be to keep the tank full? Then there would be minimal expansion or contraction?

 

[Ostsideend]

How about installing a larger water seperator? I.e.like the Sierra Part at iboats shop. It includes a vent to drain the seperation.

 

[shrew]

If it is that big of a problem, wouldn't the easiest solution be to keep the tank full? Then there would be minimal expansion or contraction…

This is not true. Fuel expands as temperature increases and contracts as temperatures decrease. While gasoline vapor is easily compressible, liquid gasoline is not as easily compressed. valving the fuel vent is a bad idea. If you are concerned about ethanol then use a marine stabilizer like Sta-Bil for marine environments along with some Startron. I treat a 100 gallon tank in fall and the boat fires right up and runs fine 6 months later.

 

[MH Hawker]

Fill the tank or use one of the many fuel treatment products around.

 

[bruceb58]

Don't worry about it. If there is water that is going to get absorbed by the fuel, it's not going to be from water vapor in the air. That amount is minimal.

Make sure the o-ring on your gas cap is in good condition. Worry about that first.

 

[Thalasso]

Try using the boat more. That in itself will take care of any water.
You would need a bigger temp. swing between day and night to create any phase separation that would cause a problem where you live.

 

[agallant80]

I think the ethanol problem mostly exists in peoples head.

 

[UncleWillie]

I think the ethanol problem mostly exists in peoples head.

That is a fair statement!!!

Lets put this water in the air issue to some real numbers.... (Simplifying all the physics involved and using common layman's units) ....

Assuming a worse case 90F Florida day; it will take 214 gallons of 100% Humidity, Fully Saturated air, to suspend one(1) ounce of water vapor.

Now, assuming a 20 gallon fuel tank that is half full. The 10 gallons of E-10 in the tank will absorb 6.14 ounces of water before separation begins.
That means the fuel would need to completely absorb absolutely all the water from over 1300 gallons of air to just begin phase separation.

There is only a 10 gallon air space above the fuel.
Then, assuming that the temperature of the air swings enough that the Air and Fuel in the tank, vary by 20 degrees every day/night.
(The ambient air temperature might need to vary 30-40 degrees to get the fuel mass insulated by the boat to move this much.)
This would cause the 10 gallon Air Space tank to breath by 3.6% every day/night.
It would take 3,750 Nights (9.8 Years) to Pump the 1300 gallons of 100% Humidity Air through the tank.

Remember this assumes 10 years of 90 degree 100% humidity weather;
and that the air going into the tank does not float on top of the heavy fuel vapors;
and that the fuel absorbs 100% of the available water vapor leaving the the tank air at 0% humidity;
and that the vapors from the 90 degree fuel evaporating fuel in the tank does not push out the incoming air.
That is a lot of assumptions.

It just isn't going to happen.

Want experimental proof?
Place a completely uncovered, open to the air, jar of gasoline in a safe place for a week.
About half of it will evaporate, but no water will be seen to have accumulated in the bottom of the jar.
Your storage conditions wont get much worse than this!

 

[Rentaltux]

I think the ethanol problem mostly exists in peoples head.

I would tend to agree on that one. Up north of the border where most of the gas has ethanol I have never heard of it being a problem. I have gas sitting for 6-8 months at a time in the summer and winter with no problems. Treat it and relax. There is other things way more important to worry about...

 

[JoLin]

Dude, it's just a poor idea that's in violation of Federal (Coast Guard) regs, You can read chapter and verse on fuel storage requirments here

http://www.uscgboating.org/regulatio...rds_partd.aspx


Here's one part that refers directly to your 'plan'

FEDERAL LAW 183.520 - Fuel tank vent systems

(a) Each fuel tank must have a vent system that prevents pressure in the tank from exceeding 80 percent of the pressure marked on the tank label under Sec.183.514(b)(5).

If you place a shutoff in the system and forget to open it, you cannot guarantee that tank pressure (positive or negative) won't exceed the legal limit.

 

[robert graham]

How about installing a larger water seperator? I.e.like the Sierra Part at iboats shop. It includes a vent to drain the seperation.

My 2nd on the idea of a separator with a clear bowl and drain petcock.....simple/efficient solution. I've used 10%ethanol gas for many years with no sign of ethanol related parts deterioration or fuel separation....but I do use Stabil and a fuel/water separator and drain carbs for extended lay-ups.....

 

[asm_]

If Willie's explanation isn't enough to convince you, here is a little ready published by EPA with detail calculation.

http://epa.gov/oms/regs/fuels/rfg/waterphs.pdf

 

[dingbat]

The snake oil manufacturers have done such a good job misrepresenting the problem to a gullible public its laughable.

Put fuel in your tank and go boating.....

 

[bruceb58]

The snake oil manufacturers have done such a good job misrepresenting the problem to a gullible public its laughable.

Agreed!!

 

[GA_Boater]

I love these discussions. :joyous: And the additive sellers hate to have their claims dashed with real facts instead of their shaky claims.

 

[oldjeep]

I love these discussions. :joyous: And the additive sellers hate to have their claims dashed with real facts instead of their shaky claims.

So what you are saying is that adding a couple oz of Propanol to 40 gallons of gas really doesn't do anything? :faint2:

 

[GA_Boater]

So what you are saying is that adding a couple oz of Propanol to 40 gallons of gas really doesn't do anything? :faint2:

Not knowingly, it's still a form of alcohol. What is it supposed to do or prevent?

 

[bruceb58]

It is a gas drier. It is more commonly called isopropyl alcohol. It's purpose is to absorb water but doesn't have the phase separation properties that ethanol does.

Both ethanol and isopropyl alcohol are going to absorb water. If you are already using ethanol fuel and you are getting enough water in your fuel that you are worrying about phase separation, you have big problems with your fuel supplier.