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old gas in tank

wwc's Avatar

Join Date: Apr 2003
Posts: 496

09-16-12, 01:20 PM   #1  
old gas in tank

I didn't get my fishing boat out this year or last year ,it's a fish and ski outboard with the tank in the hull.
it has about a 1/8 tank, should i not worry since it has oil mixed with the fuel or next year fill it with fresh fuel and run it till it's all gone or is there a way to drain the fuel out, i tried to siphon but i couldn't get anything out.

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Pilot Dane's Avatar
Group Moderator

Join Date: Mar 2003
Posts: 16,690

09-16-12, 03:12 PM   #2  
Best would be to remove the fuel as soon as possible to prevent varnish deposits from forming that can break loose and clog your carburetor(s). But, as you've found out, getting fuel out of a tank in the hull can be difficult. Siphoning fuel out can be difficult. I've used a vacuum pump intended for changing the oil of inboard engines. You can also disconnect the fuel line that goes the the engine and use it to draw the fuel out.

If you don't drain the fuel out I think you'd be OK if there is only 20% old fuel. 80% new fuel mix should dilute it enough that it will run. There is still that danger of varnish and other deposits though. You may get the engine started only to have it die as the crud shakes loose and causes trouble with the fuel filter and carburetor(s).

I'm most concerned about the condition of your engine and carburetor (s). Did you pickle or prepare the engine for long term storage? Did you run the gas out of the carbs. before putting it away?

wwc's Avatar

Join Date: Apr 2003
Posts: 496

09-16-12, 08:18 PM   #3  
thanks for the reply, Yes I did winterize the lower unit and fogged the carb and cylinders with the spark plugs out and rotated the pistons also .

Rick Johnston's Avatar

Join Date: Apr 2007
Posts: 4,239

09-17-12, 04:24 AM   #4  
It gets a whole lot more interesting if that old gas contains ethanol. Phase separation is a huge problem with ethanol in marine engines. Regardless, it's best to drain it. I pulled five gallons of phase separated gas/water/ethanol/sludge out of my port tank this summer. Wound up with one gallon of filtered gas and used it in the lawn mower. Now it looks like the starboard tank needs some attention.

I use a siphon pump from Auto Zone. (Not the one from Harbor Freight -- that cheepo doesn't work.) Once you get the siphon going the fluid comes out pretty quickly. If your tank is under the floorboards you can gain access through the fuel gauge sender.

GregH's Avatar
Super Moderator

Join Date: Jan 2001
Posts: 9,607

09-17-12, 05:08 AM   #5  
For sure you should attempt to remove all the fuel.

Not sure what is available in your area but here our top premium fuel has no ethanol and since running this in my outboard and small motors have pretty much eliminated fuel related problems.
The difference in price is more than worth it.

GregH.........HVAC/R Tech

igneous's Avatar

Join Date: Jun 2005
Posts: 236

09-18-12, 10:36 AM   #6  
Do what I did with my jet boat when I first bought it. Get a clear hose that will fit thru the drain plug hole at bottom of transom, then take off the fuel pump/sender that goes down into tank (not the hose filler tube where you pump gas in tank because of the rise and losing prime).
Not put your clear hose thru the drain plug and into gas tank, then get behind/under drain plug and siphon it out into old gas tank(s). It helps alot if you have someone to watch the flow so you don't drink any gas!
Like GregH said, if you're lucky enough to have non ethanol gas closeby, make sure to use that in your outboard/inboards. See below to find good gas.


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