To Fill or Not Fill

[Ajskier]

Good Afternoon All,

For those of us that have to winterize our boats, wanted to ask a quick question. Is it best to store the boat with a full tank of gas, either non-ethanol or stable added, or does it not matter as long as the fuel that is in the tank is either non-ethanol or has stable in it? I have heard it both ways over the years and was just wondering what is best.

Thank you,AJ

[Kelvin]

I like a full tank. Less room for condensation to form.

[Ajskier]

@Kelvin thank you, that is my train of thought, but I was having a discussion with a few members of our club and they were the other train of thought it doesn't matter as long as the fuel was non-ethanol or had stable in it.

[jpwhit]

I store filled. The change in volume of gasoline as temperature changes is tiny. The change in volume of air is significant. Over the winter if there is a lot of air in the tank it constantly expands and contracts as the temperature changes. That brings in moisture through the fuel tank vent lines. Full tank, very little air in tank to bring in moisture.

[MDB1056]

Yes add Sta-bil to a full tank . Amount is noted on the bottle

[Nando]

I always store mine full with stabilizer but it seems rare that temperatures would change so rapidly that condensation is really a concern.

[bananaron]

Non oxy gas is the best to use due to shelf life.I always use sea foam as my additive and don't store with a full tank.I have never had a problem in many years.

[PatM]

I was told it doesn't matter anymore that the tank is full. The tanks today are plastic, not aluminum and condensation is not as much of a concern.

[jpwhit]

This is interesting reading IMO. The way I look at it is I've never heard a compelling reason, that I accept, not to store it full. Plastic tanks certainly reduce condensation, but do not completely eliminate it. I run ethanol fuel during the season because it does a better job of keeping the system dry assuming you use the boat a lot. I store the boat with as much ethanol free in the tank as I can, but since I use ethanol gas during the season, there is always some left in the tank.

https://boatus.com/expert-advice/expert-advice-archive/2014/january/three-ethanol-myths-clarified

[keithh2oskier]

I always added fuel stabilizer and just left it with whatever fuel I had in the tank at the end of the season. our temperatures in CA were pretty consistent over the winter and the boat was stored in the garage so I didn't think there was big fluctuation.

[BraceMaker]

I see both sides, years ago I stopped filling the tank fully. I marked my tank for how much fuel it has so I can tell if it has 5/10/15 gallons. I treat what is in it and then run it.

From that day on I treat all my fuel in the can till the end of the season so it is all stabil treated before it goes in the boat.

Then I try to run it mostly empty. I have other uses for my canned fuel be it lawn tractor, snowblower, snowmobiles etc. So I try to run the boat as low as is safe.

Then I close the fuel fill which is well sealed and put a rubber cap on it (the through hull vent) with a hose clamp.

You can get an assortment on amazon.

[JamesMandy]

It’s best to drain the boat of the fuel before storing it for the winter. It would be best to refer to the owner’s manual of your boat to see if your exact boat requires that you drain the fuel tank. If you do store the boat with a full tank of gas, then you should at least drain in between the first use of your boat until the next season.

[brody]

I always run stabilzer through it at the end of the season before I pull it out. Then i syphon as much fuel as possible. Im in canada and have to store it from october to may. I would rather run fresh gas through it in the spring. If are worried about water in the fuel, dump in some gas line antifreeze for your first tank. Never had an issue

[Kevin89MC]

I have done it several different ways with both boats I've owned over 25 years. On my '89 MC ProStar (351 carb), it ran poorly on high octane fuel (which was the only non-ethanol fuel I could get) so I always ran it on 87 octane with 10% ethanol fuel. The only time I _didn't _keep either Seafoam or Stabil in the tank was when I knew I'd run through it within a week or 2. In the beginning I always kept it full and stabilized over the winter, and the ethanol fuel never gave me any problems. One fall I forgot to fill it up in the fall, had no problems the next spring. I also recall forgetting to have stabilized fuel in at the end one season, and still no problems the next spring either. That spring I did fill it up completely with fresh gas and Seafoam, and maybe got lucky with no issues.I usually store my '99 Response (EFI) with however much gas is in there (usually 1/4 tank as I don't like a full tank for slalom). Always stabilized for the winter, usually ethanol free (but not always), no problems so far. Obviously I think stabilized non-oxy is the best for the winter, but I tend to think fresh gas in the spring is better than burning a full tank of 6+ month old gas in the spring. So I think that having the fuel system in good shape and using good quality stabilized gas are the most important things for storage.

[Bruce_Butterfield]

This is really interesting from a theoretical point of view. Most of us anal-retentive boat owners go to great lengths to avoid ethanol related problems with stories of "I've done this and never had any problems"...

So is there anyone out there who has actually had problems specifically related to ethanol in the fuel? I haven't heard any reliable horror stories, just the normal "ethanol sucks and can cause all sorts of problems" anecdotes.

For the record, I'm no fan of ethanol and avoid it as much as practical, I just wonder if its really as bad for modern engines as some of us fear. I "think" old engines/fuel systems are more susceptible to damage.

[GaryJanzig]

If you store in a cold environment and have a metal gas tank store full. I have a plastic tank and store with 1/8 tank of gas, but with enough Sta-Bil to treat 80 gallons.

[RichardDoane]

@Bruce_Butterfield it's the alcohol's damage to rubber components that people worry about but there's not really that much alcohol in the mix, truly becoming an old wive's tale IMO,we store full w/ stabilizer/seafoam and you're good to go next spring

[Rednucleus]

I keep 5-10 gallon of unleaded in 5 gal tanks for general small motor use - mower, rototill, chain saw, string weeder. At best I refill 1-2 times a year. My old Echo saw starts once a year on whatever gas has been sitting in it for the past year by the 3rd pull. Same for all my other toys, despite all the warnings on needing "fresh gas".

[Ski2000]

@Kevin89MC I'm with you on fresh in the spring. I stabilize whatever is in the tank and fill up with fresh in the spring. Worked great with the pro sport 5.0 efi I had. We will see if it holds true for the 409 in it now.We're usually down at least 5 months here in Iowa.

[Ajskier]

I really appreciate everyone's insight into this topic. My anal retentive self filled my model year 2001 SN up with non-ethanol fuel and added stable to it, I would rather be safe than sorry.

[6balls]

complicated answers to a simple problem, owned boats for 30 years @Bruce_Butterfield :smile: and never had any problem with fuel stabilizer. Usually put it before running it to the launch for the last time so it runs thru the motor. Othewise have paid no attention to full tank vs not--regardless of whether stored in the MN cold or in the heated arrangement I eventually had.