Draining Gas In Winter

Dagojoe

Cadet
Joined
Jul 16, 2007
Messages
22
I was told once that prior to winter storage for the boat (Outside but covered) I should put in stabilizer, run the engine for a while then fill the tank completely. I was told that filling the tank helps prevent moisture. I am curious, does everyone else fill their tank or leave it empty or close to empty (assuming you are storing your boat outside).

Joe
 

BTL

Petty Officer 2nd Class
Joined
Feb 22, 2017
Messages
106
Everyone I ask has a different opinion on this. I'm no expert so I won't even try to debate the science of fuel/ethanol/water/tank material, etc. I'll just give my personal experience.

Before my last outing of the year I add an appropriate amount of stabilizer or Seafoam to the tank, and then after I pull out of the water I add a little more to whatever is left. I've left full tanks, empty tanks, and partial tanks in a few different boats and never noticed any difference in engine performance the following year, so I don't worry about it anymore.

One of my boats lives in an unheated garage in Minnesota all year, and the '97 Mercury on it runs like a champ every Spring regardless of how much gas sat in the tank all Winter.
 

Blind Date

Chief Petty Officer
Joined
Mar 5, 2014
Messages
462
I leave the tank close to empty & add fresh fuel in the spring right away when I pull it out of storage. I add fuel stabilizer on my last outing to work it into the engine's fuel system..
 

tpenfield

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Staff member
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Jul 18, 2011
Messages
17,624
'Empty' is the new 'Full' as far as fuel tank storage goes. Marine fuel tanks really do not have the opportunity to bring in moisture laden air as once theorized.

The full tank concept is theory, but not really proven. More and more people are starting to realize that and opting for more of an empty tank than a full tank.

The fuel tank, even in a mostly empty state has an abundance of fumes in it. We all know that gasoline fumes are heavier than air. So, air cannot get past the fumes to bring moisture into the tank.
 

Stumpalump

Chief Petty Officer
Joined
Dec 5, 2013
Messages
413
Don't need to do anything. It will be fine.

For those that subscribe to the full keeps out condensation...read this
http://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm

Kinda true but not the big problem with water. Ethanol is hydroscopic and does not need condensation to pull water out of the air. I get water in my gas in Arizona where it is too dry for condensation drops to form. Old school was to leave it full but with ethanol you don't fill up the tank before storage. Here is why. Say you leave 5 gallons in it and it becomes full of water. The hydroscopic properties of the gas will only pull so much out of the air and then stop. This gas is crap and best to be drained but....Ethanol fuel has one excellent redeeming quality. The ability to absorb water. What? Dump a load of fresh gas into the water laden old gas and it will absorb and burn it. Ethanol can hold a lot of water so the best way to get it out of your tank is by putting a fresh load of dry ethanol on top of it. I allways fill my tank with fresh as I'm headed to the ramp. Never after and never for storage. The one thing that's worse for fuel than wet and cold is high heat. We have that and the same principle apply. Adding fresh gas on top of old nasty gas disolves and cuts it enough to burn fine.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
2 stroke oil has a fuel conditioner built right into it, so no need for more if you are pre-mixing. Hard to make a mistake here.

It's when you are not pre-mixing things get a little dicier. Like the gas tanks used to supply 4 strokes and injected 2 strokes. Here, you are rolling the dice big time without conditioner, regardless if you plan on full or low tank.If you're on the fence, ask anyone that's had their carbs or injectors cleaned lately for their plans. Pretty easy to predict....

Last, steel tanks not used with pre-mix or fuel conditioner can and do rust if left partially full long enough. That's pretty much a fact. You can talk that over with many old car and bike collectors if you like.
 

tpenfield

Moderator
Staff member
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Jul 18, 2011
Messages
17,624
Who has got a spare fuel tank that we can put a few gallons of gas in an leave outside all winter? We'll check it in the spring time.

That would be a good test :)
 

JASinIL2006

Vice Admiral
Joined
Feb 10, 2012
Messages
5,525
Who has got a spare fuel tank that we can put a few gallons of gas in an leave outside all winter? We'll check it in the spring time.

That would be a good test :)

I do this (or something similar) every year at our cabin in Ontario. I leave several gas containers - some full, some partially full - up there. Sometimes tightly capped, sometimes with a loose fitting cap that would be similar to the conditions in a vented gas tank. I usually treat with Stabil, but not always.

Never, ever have I seen water collect in this gas. It always burns just fine in the last Spring/early Summer when I go back up there.

I've come to believe it doesn't really matter whether my boat's tank is empty or full or somewhere in between. If I was laying up for more than the season I might treat it differently, but all the evidence seems to suggest it doesn't matter.
 

Dagojoe

Cadet
Joined
Jul 16, 2007
Messages
22
wow, thanks for all the replies. Definitely different opinions. My tank is small(fiberglass 25 gallon tank). I bought a small trolling motor this summer with a separate tank so I hardly use my main motor/gas anymore. The gas I have in my main tank is from last winter's fill-up before I stored it for the winter(With plenty of stabilizer). Fortunately I have very little gas left in the 25 gallon tank. I may just add a little more stabilizer and run the rest of the gas out before winter and start with a fresh stabilized tank in the summer. Thanks everyone for your opinion!!!!! Joe
 

JimS123

Fleet Admiral
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Jul 27, 2007
Messages
7,952
Last, steel tanks not used with pre-mix or fuel conditioner can and do rust if left partially full long enough. That's pretty much a fact. You can talk that over with many old car and bike collectors if you like.

I treat my boats like babies. Stabilizer, SeaFoam, etc. If the lawn mower craps out I can sit down and have another beer and cut the grass tomorrow. If my boat fails on vacation it's a major catastropy. Vacations come only once a year.

I have a metal gas can that I use for my tractor, lawn mower and rototiller. I put in whatever crap is the cheapest at the pump. I don't use stabilizer ever. The tank is rusty on the outside, has scratches and paint loss, but the interior is shiny with no rust. It sits empty or half full most of the time, in an outside unheated barn. I bought the gas can in 1968. I guess I'll do something different from now on...
 

BRICH1260

Lieutenant
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Jul 6, 2011
Messages
1,342
For no longer than it will be stored, don't worry about the fuel level. Just be sure and well treat the fuel in there.
 

wahlejim

Master Chief Petty Officer
Joined
Jul 23, 2015
Messages
884
There is no need for stabilizers, additives, oil, etc. unless it is sitting for more than a year.
 

frantically relaxing

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Joined
Nov 19, 2011
Messages
699
The only way water can get into a stationary gas tank- other than a kid with a water hose or the water that came with the gas- is if the air in the tank continually changes places with humid outside air. Only way that will happen is on purpose ;)

I've never had gas problems. My FIL drove his motorhome, from an RV park where it sat 10 years, 55 miles to his house. The exhaust stunk to high heaven, but the old 460 had no trouble running with it. My Party Cruiser's generator started every year for 7 years on the same gas. The reason it didn't start on the 8th year was an ignition problem.
 

444

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Joined
Jul 16, 2010
Messages
704
I never have worried about fuel level in the tank during storage. I have an old muscle car and on the forums a lot of guys say the same thing, fill it to prevent moisture and rust. I never have worried about it. I've had a couple rusty tanks, they have always rusted out from the bottom on the outside never at the top or from the inside.
 

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
There is no need for stabilizers, additives, oil, etc. unless it is sitting for more than a year.

Except that you can't guarantee that won't happen. Illness or injury could keep you off the water for a season. In late September, 2015 I gassed up for the last time that season and stabilized the fuel. Used it for a few more weekends and hauled it out in mid-October.

Fast forward to 2016. Lousy spring weather prevented me from launching until June. Lousy summer weather prevented me from using it much. In August I was still running on the same 10-11 month old fuel I put in the previous September.

I stabilize what's in there at the end of every season. I also do the annual fall oil changes, grease the couplers and everything else, and winterize everything with the thought that the boat could be out of the water for longer than just that winter.

My .02
 

Maclin

Admiral
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May 27, 2007
Messages
6,761
I put stabilizer in at each fill, have never had any runability problems or performance issues. This way it is all the way through the fuel system all the time. I started doing that during one point in boating where the boat was stored a long ways from where I lived and I never knew what the last run would be for the season. I could make a special drain-the-engine trip and not have to fuss with the fuel.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Agree with Bruceb58 on this one, never really had a problem with it. I'd be more worried if it was diesel.
That said, if it helps...more recently before storage I have ran the tank fairly low with super unleaded petrol and a slight dose of 2 stroke.
This year I'm planning on a slightly higher dose of 2 stroke in the tank.
 
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