Boat away for the winter: full gas tank or empty?

[KawarthaAngler]

Hi.

 Was curious what guys do when putting boat away for the winter.  Do you fill the tank and put stabilizer in the gas, or do you let the tank run almost dry and just put a small amount of stabilizer in the gas?

 I have been told to fill the tank in my boat (100L tank) and then stabilize the gas because that helps prevent moisture building in the tank over the winter.  I've also see people put their boat away for the winter and it has very little gas in it so come the spring they can put a fresh full tank in it.

 What you do?

Thanks!

[DRIFTER_016]

My boat usually gets put away full or very near full.

I use stabilizer in every tank full but add a little extra when I put the boat away for the winter.

 

[AKRISONER]

full tank and absolutely no ethanol...91 premium ethanol free with stabilizer

[Raf]

i run stabil through her, disconnect the tank, dump the remaining fuel in wife's car and put the tank in the shed.  next spring, i fill the tank with fresh fuel. 

doesn't help you, but that's the beauty of portable tanks.

[KawarthaAngler]

Ya, for my small tin can ... I stabilize the fuel that is still in the tank and leave it in the shed for the winter.  Usually I like to have as little as possible in the tank. In the spring I add some fresh fuel to it and I'm good to go.

But for the Fish & Ski boat with built in tank ... can't do that. 

Edited November 20, 2017 by AdamWoodhouse

[chris.brock]

For a big in board tank like yours I would go full, like other guys have said, stabilizer (ran through the fuel system ) and premium, no ethanol, it might be a good idea to absolutely make sure the gas has no ethanol, it could be a 100 liter mess in the spring 

[mike rousseau]

I fill up after every outing year round

 

tjis late I run stabilizar in every tank cause you never know what tank is your last 

[Mister G]

10 hours ago, mike rousseau said:

I fill up after every outing year round

 

tjis late I run stabilizar in every tank cause you never know what tank is your last 

I do the same.........I hate when I go with someone's boat and they stop for fuel on the way to the launch......grrrrrrrr

With the plastic fuel tanks I don't think moisture is a problem like in the past but I still fill up my boat and run 2+4 through it starting in late October.

[KawarthaAngler]

Thanks for the input.

[Old Ironmaker]

I have heard guys put them away anywhere from MT to full and everywhere in between. I use ethanol free gas and fill it and out in some gas treatment.

[jimmer]

Does gas without ethanol still need the stabilizer?

[DRIFTER_016]

2 hours ago, jimmer said:

Does gas without ethanol still need the stabilizer?

Yes. It keeps it from breaking down and causing varnish in the fuel system that can clog up carbs and injectors.

Ethanol fuels will do the same but they have the added problem of phase separation and water absorption.

 

Edited November 21, 2017 by DRIFTER_016

[mike rousseau]

4 hours ago, jimmer said:

Does gas without ethanol still need the stabilizer?

I was told gas loses octane levels over time... I was told stabilizar helps keep octane levels

[smitty55]

17 minutes ago, mike rousseau said:

I was told gas loses octane levels over time... I was told stabilizar helps keep octane levels

That is my understanding as well. Gasoline begins to degrade basically from the time you pump it.. Stablilizer stops the the octane level from dropping and in the case of seafoam also cleans and prevents phase separation.

Drifter I was told by a small engine shop owner that even with a stabilizer in the fuel that carbs left with fuel in them will still create varnish as the fuel evaporates over time. I use SeaFoam in all my premium small engine fuel but still run the carb dry before storage for any length of time.

 

Cheers

[floater]

I tried putting my Whaler away with a partially filled tank and it separated over the winter and stopped both motors in the spring! I went out for the last time this season and ran the main tank dry and switched over to a portable tank. I'm going to pump out the remaining gas in the main tank soon and put her away dry.

[Mister G]

32 minutes ago, floater said:

I tried putting my Whaler away with a partially filled tank and it separated over the winter and stopped both motors in the spring! I went out for the last time this season and ran the main tank dry and switched over to a portable tank. I'm going to pump out the remaining gas in the main tank soon and put her away dry.

Right from BoatUS article :

Winterization and What You Need to Know About E-10 Gas Putting a Boat Away for the Winter? What You Need to Know About E-10 Gas. 




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.

[DRIFTER_016]

16 hours ago, smitty55 said:

That is my understanding as well. Gasoline begins to degrade basically from the time you pump it.. Stablilizer stops the the octane level from dropping and in the case of seafoam also cleans and prevents phase separation.

Drifter I was told by a small engine shop owner that even with a stabilizer in the fuel that carbs left with fuel in them will still create varnish as the fuel evaporates over time. I use SeaFoam in all my premium small engine fuel but still run the carb dry before storage for any length of time.

 

Cheers

Never had that issue and my boat was stored for 7 years with stabilized fuel at one point.

Engine fired right up after 7 years in storage with 7 year old fuel.