How do I get old gas out of a tank that under the deck?

rider1

Seaman Apprentice
Joined
Jul 11, 2004
Messages
31
Hey guys,
I have a 1999 Sailfish with a 50 gal. stainless tank under the deck. The boat has set for 4 years, and only has a few gallons of gas in the bottom of the tank. I wanted to see what it looked like, before I filled it up and put it back in the water.
So, I took the fitting of the fuel line, and pumped A little gas using the ball into a clear jar. I set the jar on my work bench and let it set for about an hour. When I took a look at it, there was an off color looking substance in the bottom of the jar. It looks like water but I don't know.
I had stabilizer in the old gas and oil mix, and I thought that maybe they had separated. Then again I don't know.
I thought that it would be safer, if I took out all the old gas and start fresh.
Can some one tell me how to get all this old gas out of this tank?
Any help would be grateful,
Rider1
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: How do I get old gas out of a tank that under the deck?

A pump or a siphon with a weighted tube that will stay on the bottom. I would try to tilt the boat up if possible to get all the gas/water/debris/whatever down in the end you're draining from. Then maybe add a few gallons of fresh gas to flush it out some more. Install a fuel/water separating filter, fill tank with fresh gas, run it and keep dumping/changing that filter until it's pretty darn clear. As long as your filter cartridge is there, then the junk can't make it's way to your motor, and you can deal with the cartridge. Stainless Steel tank is good! Good Luck
 

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: How do I get old gas out of a tank that under the deck?

The fuel that you are getting out with the primer bulb is coming "almost" from the bottom of the tank as the pick up tube in the tank will only be about 1/2 inch off the bottom, so with the nose of the boat raised you will probable remove about 98% of the fuel and a good RACOR type filter will stop the other junk and you can drain that.
 

10thHawk

Petty Officer 3rd Class
Joined
Sep 13, 2009
Messages
96
Re: How do I get old gas out of a tank that under the deck?

You can also disconnect the fuel line from the engine and use an inline fuel pump. I did this with mine last year and it worked great. Bought a few five gallon gas cans and filled them up with the old gas.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: How do I get old gas out of a tank that under the deck?

If its long enough put the hose over the side till its below the tank.Use the primerbulb to start it to syphon. Add a filter as suggested.Add something like seafoam to the new fuel as a normal procedure.It will retard aging etc.
 

rider1

Seaman Apprentice
Joined
Jul 11, 2004
Messages
31
Re: How do I get old gas out of a tank that under the deck?

Many thanks again!
I sure like this site, and the good help that all of you provide.
Have a nice night.
Rider1, out
 

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: How do I get old gas out of a tank that under the deck?

the gas you have, is showing water, which is often from phase seperation--the bad thing that ethanol does.

There are dozens of posts about cleaning tanks here if you want more detail. A couple of my suggestions:
If you can, run your fuel line out through the bilge drain plug and into the jugs, rather than up and over.
Clean the tank by spraying a can of carb cleaner in there. Wash it around by lowering and raising the trailer, or going for a wild drive.
Remove the sending unit and swab the tank out with a rag securely fastened to a stick.
 

wifisher

Chief Petty Officer
Joined
Mar 9, 2011
Messages
578
Re: How do I get old gas out of a tank that under the deck?

Home cookin, I don't mean to nit-pick here, but would like to clarify a little. Ethanol does not cause phase separation. It does, however, make it much more evident. Phase separation is caused by water in the gas. Usually caused by sitting in the tank for an extended period of time with the tank less than full. The temperature fluctuations cause condensation inside the tank, which becomes water in the gas. A full tank has no(little) air and therefore no condensation. The water in a tank with MTBE (pure) gasoline mixture will settle to the bottom of the tank and stay there until removed. In an ethanol blend, the water will dissolve into the ethanol. If there is very little water, the ethanol will remain soluble in the gasoline, and no ill effects are noticed. The problem is when too much water enters the mix, the ethanol is no longer soluble in the gasoline and will settle to the bottom. This causes the water plus 10% of the fuel to settle out instead of just the water.

Bottom line, what I'm getting to is, if you are going to let your tank sit for a period of time, your tank should be either empty or full, and it will reduce phase separation, and water in the fuel by quite a bit.
 

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: How do I get old gas out of a tank that under the deck?

Most experts are now saying to empty your tank instead of leaving a full tank. Kind of hard to empty some big tanks. I have 75 gallons on my new tank, the old one was 115 gallons. I do use the new fuel treatment designed for ethanol.
Startron has an excellent brochure out that explains it all. go to www.startron.com and read for yourself.
 
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