Maintaing an empty fuel tank

[timjet]

The aux tank located below the swim platform makes my already aft heavy boat even more so when filled with fuel. I have used most of the fuel in the tank and am considering not putting any more fuel in it. I don't think I will need the tank for some time so I want to "moth ball" it so to speak.

What should I do to keep the tank from growing bad stuff with the little bit of fuel in it. Should I pump it out and put some treatment in it.

 

[C lectric]

Yes.
My opinion only but I would add a stabilizer to slow the deterioration of remaining fuel. There will be some. Then pump out whatever you can get .


Don't use an alcohol based stabilizer.


If the tank is to remain empty for a long time, a year, then you might want to refresh with more stabilized fuel. Only need a few gallons and then pump it out also.
Take a good look for any sign of water when pumping.

When emptying get as much fuel as possible.

 

[FF]

Drain it completely .

Before putting it back in service put in a couple of G of fuel and drain that.

 

[psneeld]

What is it made of? Plastic /aluminum...pump it out to the last drops if able. Steel...not sure what's best. Just cut mine up/out and there was some but not a lot of rust despite being empty for the better part of a year...mostly covered with (asphaltines?)...probably best to fill with inert gas)

If you just want to keep it simple...you really can't...you are always rolling the dice when leaving even a little fuel unused for a length of time. If you can estimate how much is left...putting in biocide and stabilizer is a good idea...then when you go to use the tank...fill it...put in a cetane booster and run that tank first with extra filters on hand. You may get lucky depending on how long you let it sit.

If you want to do the effort to get it clean before you use it...FF's suggestion of a few gallons then pump would probably help if you can agitate it a bit first.

 

[RickB]

What is it made of? Plastic /aluminum...pump it out to the last drops if able. Steel...not sure what's best. .

Finally someone asked the right question.

No matter what it is made of, pump it bone dry. If it is steel and won't be used for a couple of years, fog it with the type of preservative oil you would use in your engine.