Gas before or after storage

Throttle1971

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Pulling boat this weekend. I usually fill up both tanks and put in stabilizer. Do you all do the same prior to storage or wait until spring?
 
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Kizuna

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I used to fill and put stabilizer, until I got a bigger boat that holds a lot more gas. Also the gases can expand with heat and create unwanted pressure with full tanks. I now add stabil 360 with every fill up throughout the season and try to leave less than half tanks before the boat is pulled.
 

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I keep both my boats around 1/2 tanks during the year. I dont need the extra weight. I add stabilizer and fog em up. All good in the spring
 
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seasick

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I haul and store with whatever gas is in the tank, usually about 1/4 tank, this year both boats will have more due to less boating last year. One thing that is important in my mind is that you add the stabilizer before you pull the boat, preferably before the last outing. That allows the gas and stabilizer to mix and also gets the stabilizer into all the fuel system components. I do fog the motors or spray fogging oil into the spark plug holes and manually rotate the crank. One model engine is easy to fog the cylinders directly, the othe model motors are a bear to remove the plugs so I fog using the aerosol can into the air plenum. As part of my winterizing, I also drain the motor mounted filter and the VST tank if present. I do not remove/replace or drain the remote gas filter until next season AFTER I start the motor.
 

Punchline Cap

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My boatyard where the boat is stored requires at least 3/4 of a tank of gas when going into storage. I always top it off before it goes into storage. I do the same with my lawn tractor, i fill it up and put Stabil in it for the winter. A full tank of fuel prevents condensation from forming with temperature changes.
 
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PointedRose

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A full tank of fuel prevents condensation from forming with temperature changes.
Agree - fill to about 7/8 of a tank, add stabil for the off-season. Prevents excess condensation and then water in fuel by having a full tank of gas.
 

seasick

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This topic comes up every fall:)
I think that the location of the vessel, specifically the local weather is a big factor. I am in the NYC area where normally winters are cold and humidity is low. The sun is low in the sky and that also reduces heating of boats. I have stored my boats for 15 years with usually empty tanks. Stabil - yes but only during the winter. Have I had any water in the gas issues? Nope.
The problem with the discussion is that for everyone who says they fill their tank, there is another who says they don't.
If I had my boat in Florida or a similar climate, I might approach things differently but here in NY, all options seem to be fine.
I feel that I would rather store with as little gas as practical because should anything go south like a water intrusion problem caused by perhaps a defective o-ring, I would put as little gas at risk as opposed to contaminating 100 gallons of fuel at $4 plus a gallon .

I am curious why a boat yard would require 3/4 full tanks for storage though unless it because they sell the gas:)
 
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family affair

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My $0.02:
Because our 270 has way more fuel capacity than we need 99% of the time, I talked to a guy who does tank cleaning and fuel polishing for a living. Specifically we discussed how to preserve the auxillary tank. In the conversation fuel storage came up. As mentioned by others, he advised either roughly 90% full or empty. Empty surprised me untill he explained why. He has never seen an aluminum tank corrode on the inside from condensation. Every failure he ever saw was from the outside in. He said any condensation from an empty tank will easily get picked up by a water separator. Also, adding fuel to the empty tank will also "pick up" some of the moisture that the engine will burn without issue, especially if a quality fuel additive is used.
 
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nuclear

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Located in NY and I always fill at the end of the season. Go to THT and these threads go on for many, many pages. Seems there is no perfect answer so just do whatever works for you.
 

DennisG01

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As noted (especially with aluminum tanks, less so with plastic), the risk is condensation. So best practice is either full or empty. Whether or not condensation happens is going to, like Seasick mentioned, depend on a large number of factors. Could a tank be fine with a half tank? Sure. But in comparison, it is a safer bet to store full or empty. With the proper stabilizer, the gas will be totally fine come Spring - quite honestly, even the following Spring.
 

drbatts

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I start adding startron with the last couple of fill ups in the fall. Try to burn as much fuel off as i can before winter storage. Then put fresh gas in both tanks in the spring. Been doing this for 15+ NE winters.
 
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seasick

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I knew this topic would get argued to death:)
May I ask what the goal is? Is it to reduce water contamination of the fuel or is it to reduce potential corrosion of the tank?
 

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I start adding startron with the last couple of fill ups in the fall. Try to burn as much fuel off as i can before winter storage. Then put fresh gas in both tanks in the spring. Been doing this for 15+ NE winters.
I have done about the same thing for the last 24 years without any problems. I have always used Prig-g gas treatment with every fillup. I rebuilt my carbs about three years ago. I found zero buildups of any kind in the fuel lines. I have always thought that starting out with fresh gas was the way to go.
 

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Maybe one of our resident chemists can chime in on this one, but I would us caution running a tank low, but not empty with e10. A lot of condensation with a little e10 could cause phase separation even if treated. Topping off in the spring does nothing to rid the tank of the pure ethanol sitting at the bottom of the tank.
 

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I've always filled for longer storage in the hopes of less condensation buildup inside the tank. I had Hondas until recently and always used 87 and an ethanol treatment every time I got gas. Never had any fuel issues with those Honda 225s. I got Yamaha's now (250s) and haven't figured out if I need to get ethanol free fuel or just keep doing what I've done with the Hondas for over a decade. My reasoning was there are millions of Hondas on the roads burning ethanol fuel with no problems and the 225s have the same block as the Odyssey. Yamaha doesn't have any vehicles on the road so I might get ethanol free for them.
 

DennisG01

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I've always filled for longer storage in the hopes of less condensation buildup inside the tank. I had Hondas until recently and always used 87 and an ethanol treatment every time I got gas. Never had any fuel issues with those Honda 225s. I got Yamaha's now (250s) and haven't figured out if I need to get ethanol free fuel or just keep doing what I've done with the Hondas for over a decade. My reasoning was there are millions of Hondas on the roads burning ethanol fuel with no problems and the 225s have the same block as the Odyssey. Yamaha doesn't have any vehicles on the road so I might get ethanol free for them.
Motorcycles... snowmobiles... generators... and whole slew of outboards running ethanol fuel. You're over thinking it - it'll be just fine. Besides, it ain't about the block - it's the rubber components and such that can suffer. It certainly won't hurt to use E-free, but there's really no need.
 
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I have owned boats in Rhode Island, for more than 40 years, both gas and diesel. I have never topped off the tanks and never had a water problem. I add fuel stabilizer at every fill up and change the filters at least once a year. The off season is to long to have all that extra fuel sitting around for 5 months.