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What You Need to Know About E-10 Gas


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I know that many of us have already put their boats away for the year, but I received this in an eMail from BoatUS and thought it would be good information for GLF.

I have been holding off, hoping to get one or two more trips in but so far the weather has not cooperated. With gas prices now down to around $3.30/gallon I'm seriously considering topping it off adding the Stabil and getting it ready for winter in the pole barn. The first big snow storm out west means it isn't too far from that time here too. :(


Putting a Boat Away for the Winter?

What You Need to Know About E-10 Gas

ALEXANDRIA, Va., October 23, 2012 - Nearly full tank or nearly empty tank? That is the big question facing boaters now in the midst of preparing their boats for the long winter hibernation. The concern is ethanol - an octane enhancing gasoline additive that has some unfortunate, harmful side effects on marine engines. Boat Owners Association of The United States (BoatUS) has some tips learned from fuel industry insiders on how to store a boat with E-10 gasoline (containing 10% ethanol) over the winter.

  • The octane issue: Some boaters choose to leave their boat's gas tank mostly empty over the winter, and then refill in the spring in the hopes of "refreshing" the fuel to regain any octane loss. However, a nearly empty gas tank introduces a bigger problem: the strong possibility of phase separation with the E-10 gas. Incidentally, over long winter storage periods, E-10 gasoline loses octane at about the same rate as non-ethanol gasoline.
  • The path to phase separation: Ethanol (an alcohol) can attract and absorb water - about 10 times more than regular gasoline - and still burn harmlessly through the engine. However, there comes a tipping point when the ethanol can no longer absorb the water, and the alcohol will separate out or "phase separate" from the gasoline. When this happens, the solution of water soaked ethanol will settle to the bottom of the tank, which is where the engine's fuel system pick-up is located. Can you see where we are headed with this?
  • More water, less absorption: The problem with leaving a tank mostly empty is that it increases the tank's "lung capacity" to breath in moist air (water) through the tank's vent. If the tank is mostly empty over the winter, there will also be less E-10 gas in the tank to absorb the moisture. This combination of more water and less capacity for absorption greatly increases the chances of phase separation. Adding fresh gasoline in the spring would not remedy the problem - the phase-separated ethanol remains separated at the bottom of the tank.
  • The Water Separator issue: E-10 can hold up to 1/2 percent of water by volume and up to that concentration the water molecules will dissolve in the gasoline forming a soluble mixture that will pass through a water separator and burn harmlessly in your engine. The only time water will collect in a tank and not be absorbed is if phase separation has occurred, and by then it will be too late. A water separator is not a solution to the phase separation problem.
  • The Fuel Additive issue: Fuel additives are good for many reasons and should be used when laying up a boat for winter, but no additive will stand up to a good-sized slug of water. And once too much water has entered the tank and the gas has begun to phase separate, no additive will return the fuel to its original state. The only solution to phase-separated gas is to have a professional drain the tank and start anew.

The best advice for storing E-10 in your boat's gas tank over winter:

Keep the tank nearly full. This greatly reduces the volume of moist air that can enter the tank via the fuel tank vent when temperatures fluctuate in the fall and spring. With any fuel, an antioxidant (found in many additives) will help keep it fresh during lay-up. Finally, never plug up a fuel tank vent - it creates pressure that could cause dangerous leaks in the fuel system.

For more information go to http://www.boatus.com/seaworthy/ethanol.asp. A free, downloadable winterizing checklist is available at http://www.BoatUS.com/seaworthy/winter.

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Or you can leave the tank completely empty. the past three years I have been doing this with zero issues in the spring.

I pull the fuel line off just in front of the separator, using a hand pump I transfer all fuel into my SUV. last year took a while as I had over 20 gallons to hand pump out.

Keep pump until you suck air. had less than 1/2 gallon left in tank

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I was thinking of doing that too John. I have close to 30-40 gallons in mine, it's been treated for hibernation and everything. I have not had any issues since I've owned the boat. I have always left close to a full tank in it and treated with Stabill. This year my goal was to try the opposite, and burn almost all of the fuel out of it, but that didn't work out as planned.

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I was thinking of doing that too John. I have close to 30-40 gallons in mine, it's been treated for hibernation and everything. I have not had any issues since I've owned the boat. I have always left close to a full tank in it and treated with Stabill. This year my goal was to try the opposite, and burn almost all of the fuel out of it, but that didn't work out as planned.

I have left mine 1/2 full before and treated with Stabill. had issues in the spring.

I'm sure you have to do one or the other. For me just burn the gas in the fall and start the spring with a fresh tank.

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Now that our Government has decided that those of us living in large cities need to only have gasoline that contains 10% Ethanol boat owners have been faced with many questions on what is the best way to use E10 fuels.

Daily use isn't too much of a problem with newer gasoline engines though engines from he 50's and 60's have had issues. Storage of a tank of E10 fuel is what most guys wonder about at this time of year.

I did some research and thought this point should be added to what has already been posted on storing for winter.

Store fuel tanks approximately 7/8 full, minimizing the amount of air space above the fuel inside the fuel tank. Note, storing completely full may allow some fuel spillage as the fuel expanded during hot weather.

Do not attempt to seal a vented boat fuel system. The inability to vent could cause damage to the fuel tank or other fuel system components.

A fuel stabilizer should be used with E10 fuels as well. Use the stabilizer of your choice as recommended for regular use and for long term storage, E10 fuels are not as problematic in our cars and trucks because we change the fuel in those tanks pretty much weekly.

I use StaBil Marine at the regular use dosage rate every time I add gasoline during the season. For winterizing I add Marine StaBil to the remaining fuel I calculate in the tank at the long term storage dose. My fuel tank is 80 gallons and I'm uncomfortable about storing that much fuel in my garage.

I've never had a problem storing 25 gallons of E10 fuel for 9 months at the recommended long term storage rate.

One other point is to use the gasoline grade one above your engines recommended octane range when fueling up for winter as ALL gasoline loose octane levels over storage.

Contrary to the BoatUS tips on E10. Outboard motor manufactures such as Yamaha, Evinrude and Mercury do recommend moisture separators to minimize phase separation issues.

From Yamaha:

Q. . Can phase separation be reversed?

A. No, there are no additives or processes that will recombine phase separated ethanol and gasoline.

Q. . Can I use the gasoline remaining after removal of the phase separated water and alcohol?

A. No, as mentioned above, the remaining gasoline will have a lower octane level that may not be compatible with your engine.

Q. How long can E10 fuel be stored?

A. There are many different opinions concerning how long it is ok to store any fuel (E10 fuel or gasoline), 2 weeks, 90 days, 1 year, or longer, before losing the properties that are required for proper and safe operation of your engine. There are too many variables (e.g., the age of fuel when purchased, temperature, humidity, use of stabilizers and the type of storage containers) to accurately predict how long.

Q. What can I do to prevent issues with E10 fuel?

A. Total prevention of issues may not be possible but there are steps you can take to minimize the occurrence and severity of the negative affects of E10 fuel:

• If at all possible, do not use E10 fuel.

• Ideally (before switching to E10 fuel) have your fuel tank completely drained to remove any accumulated water. As little as 16 oz. of water can promote phase separation in 25 gals of E10 fuel. The result would be 2.75 gals of unusable ethanol and water mixture on the bottom of the tank.

• Install a 10-micron water separating/fuel filter between the boat’s fuel tank and the engine.

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