Gasoline -ethanol time in tank?

Willit float

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Gasoline storage time guidelines for fuel-gasoline to begin going bad ?
Ive read over the years from other online info about the ethanol based gasoline going bad after sitting in a fuel tank for extended periods of time.
So I recently rebuilt by boat, installed a new Moeller tank, all fuel lines new high quality, new fuel filter system, fuel pump, lines and carb rebuild.
Two years ago we filled the tank about 80% added fuel stabilizer and lead additive as it’s a 1977 Mercruiser 165 GM in-line 6.
So ran the boat occasionally, added new gas at the rate of about ten gallons per add and did that twice over two years. I routinely give the gas a mix by either pulling the boat or raising and lowering real quick to slosh mix.
So yesterday I rigged up a back up fuel pump-hack and hooked up to the fuel line and pulled out ten gallons.
The bad looks, smells and seems perfectly fine still. I’ll be using it in the riding mower and blend a few gallons into the truck.
Are my concerns warranted or am I just overly worried about the gas turning into clumps in the tank. Pretty sure I’ve read from other boaters that this should be done yearly ?
 

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GA_Boater

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Save some money by skipping the lead additive. 1977 motors had hardened valve seats with no need for adding lead to the fuel.

The best prevention of "clumpy" gas to to use the boat. If I read right, you filled the tank 2 years ago and since then added 20 gallons, 10 gallons at a time. In the unlikely chance your gas does go bad, adding fresh gas to bad only makes more bad gas. Keep that in mind.

How much does your tank hold? Use the boat more and if you suck gas out for a quality check, suck from the bottom. That's where the crud is. If the gas is clear, smells like gas and not varnish - It's still good.

After sending this reply, the thread will be moved to the non-repair section as it's a general question.
 

mikkydee

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Feb 20, 2015
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I am also interested in this topic about how long gas will last before going bad. Should I be concerned in gas left over from the previous fall that sat through the winter in my garage?
 

GA_Boater

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In your garage, the storage tank should be sealed, so moisture can't get in. It won't go bad.
 

dingbat

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I am also interested in this topic about how long gas will last before going bad. Should I be concerned in gas left over from the previous fall that sat through the winter in my garage?

The longest I've left gas in the boat is almost 1.5 years. Topped off the tank (~45 gallons) and went boating with no ill effects.

I have stored varying fuel tank levels (30-70 gallons) over the past 20 winters (4 - 6 months) with no ill effects.

FWIW: The boat is stored outside (15 to 100 degrees F), in high humidity levels (on the coast), year around. E10 fuel only
 

Willit float

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Mar 15, 2020
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Save some money by skipping the lead additive. 1977 motors had hardened valve seats with no need for adding lead to the fuel.

The best prevention of "clumpy" gas to to use the boat. If I read right, you filled the tank 2 years ago and since then added 20 gallons, 10 gallons at a time. In the unlikely chance your gas does go bad, adding fresh gas to bad only makes more bad gas. Keep that in mind.

How much does your tank hold? Use the boat more and if you suck gas out for a quality check, suck from the bottom. That's where the crud is. If the gas is clear, smells like gas and not varnish - It's still good.

After sending this reply, the thread will be moved to the non-repair section as it's a general question.

The tank is a 47 gallon Moeller FT4704, the gas that came out looks perfect. Pretty sure the engine has a decal that says to run leaded gasoline but I'll double check that. Think I read somewhere that as long as there are not contaminates, failing lines, water etc that blending fresh gas will help. I imagine like you said the key is to use the thing and burn it up.
I am pulling the gas out through the fuel feed line in the tank that goes through the fuel filter and am tilting the boat down to put more volume in the location of the pick up.
 

GA_Boater

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It took a long time before marine motor builders said E10 was acceptable. Same with leaded gas, lead additive is not needed. Mercruiser updateded fuel standards for unleaded first and later to E10, but owners manuals and decals weren't sent to owners.

Water is heavier than gas and sinks to the bottom. Adding fresh gas doesn't change that. Gas does go stale, but it takes a long time and there is no fixed time because of variables like temperature.

Asked about the tank size more out of curiosity. Keeping a tank full is one of the ways to minimize the chances of humid air eventually making the bottom crud. If the fuel system is in good shape, the tank vent is the main source for humid air into the tank caused by expansion and contraction due to temperature changes.
 

Scott Danforth

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i have had gas go bad after 6 months
i have had gas last over a year without going bad
the problem is, it depends how long the fuel was in a bulk tank prior to getting transported. the storage temperature, the additives injected at point of distribution, any contaminants in your tank, exposure to elements, sealed vs un-sealed containment, etc.

best advise...... use the boat often.
 

JimS123

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E-10 going stale is a myth. ALL gas goes stale, not just E-10. I have an Owner's Manual for a 1955 Mercury outboard and even way back then they recommended using stabilizer over Winter layup.

Our current experience is that gas can last up to 2 years, if stabilized in the beginning and stored in dry conditions and with a full tank.
 

dingbat

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IWater is heavier than gas and sinks to the bottom. Adding fresh gas doesn't change that.
Not unless you use E10....one of the benefits of E10 is that it hygroscopic.

Depending on the temperature of the fuel, not ambient temps, E10 can absorb water up to 0.5% by volume.

Putting 100 gallons of fresh, 60 degree E10 in the tank will absorb up to 1/2 gallon of water off the bottom of the tank.
 

Lou C

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that is true as long as the amount of water does not exceed a set point, if it does, then you can get phase separation where the water + alcohol drop to the bottom of the tank.
I've never had this happen, just maintain your fuel system well, make sure your gas cap gasket is not all dried out, I replace them every few seasons, also make sure you do not have water pooling right on top of the sending unit for the gas tank, that can cause corrosion in that area and eventual leaks. I've used 2 year old stabilized E10 gas with no problems on a carbed engine.
 

hnt

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Dec 31, 2010
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I have used E10 for years and never add stabilizer and I just leave whatever amount is in the tank at the end if the season. I always change the fuel filter in the spring and dump it out to check for problems. Never have had an issue. I put in 50 gallons in new E10 87 in my tank today and went out for the first time this year and she ran like a a top
 

hnt

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And I paid $1.99 a gallon which in NY is amazing. I will try to burn my share this year
 

TyeeMan

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Rather than totally filling a large tank when you know your're not going to use the entire quantity in a few outings and worrying about the fuel going bad, don't totally fill the tank. Any outing I can usually guestimate how much fuel I'll use, so I add X amount plus maybe a little more every time I go out and I'm good to go. So I'm always adding fuel over the course of the boating season. And at the end of the season I try and run the fuel down to at least a 1/4 tanks or less for winter layup.

I know, there is tons of discussion about leaving the fuel tank full or empty over winter layup. But doing what I'm has been working for me for quite a while.
 

JimS123

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Rather than totally filling a large tank when you know your're not going to use the entire quantity in a few outings and worrying about the fuel going bad, don't totally fill the tank. Any outing I can usually guestimate how much fuel I'll use, so I add X amount plus maybe a little more every time I go out and I'm good to go. So I'm always adding fuel over the course of the boating season. And at the end of the season I try and run the fuel down to at least a 1/4 tanks or less for winter layup.

I know, there is tons of discussion about leaving the fuel tank full or empty over winter layup. But doing what I'm has been working for me for quite a while.

Mercury Marine recommends filling the tank. They also recommend stabilizer. They recommended the same thing back in 1955. So there!!!

Some fill, some don't, some have problems, some don't.

Its all about the storage conditions. Put your boat in a nice dry garage and cover it. Or, leave it outside in damp conditions and don't cover it. Live in a high humidity area, or a low humidity area.

There is no simple answer.
 
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