View Full Version : Emptying a boat fuel tank

AI Inc
08-12-2008, 07:49 AM
I have a 23 yr old boat that ive been having ethenol problems with. The ethenol has loosened all the crud in the old tank.
Im putting a reserve tank in to use as a main tank and just abandoning the old tank. I want to pump out the old fuel for several obvious reasons .

Any ideas on getting old fuel out of tank?

08-12-2008, 08:14 AM
I had a similar situation years ago. It was a 25-year-old boat and I wanted to replace the 18-gallon tank. But first I had to remove the old one, and before doing that, it had to be drained since it was still half filled with gasoline. I simply siphoned it out when the boat was on the trailer. At the time, I had a few 5-gallon jerry cans to put the old fuel into. Seemed like the obvious course of action for me to take. I don't see why you even ask that question unless you have a very large boat with several hundred gallons still in the tank. But good luck with it.

AI Inc
08-12-2008, 08:20 AM
did ya do the old stick it in your mouth ans suck suction? Done it plenty of times as a kid , the thought now makes me want to puke thou. Was wondering if I could hook a hose to the fuel pump and just crank the motor.

08-12-2008, 08:26 AM
A.I., How about AI?(AIR INJECTION), I have a ball valve off my air compressor that I hook up to a male or female coupling to fill or drain liquid and air, depending on what is needed. On 55 gallon drums, I took the large bung,drilled and tapped it for a air fitting and it only takes a little air tank I took off of a dump truck to empty the drum, just be careful to not over fill at first with air, you'll know cause it will push the drum lid up under pressure. It only takes a couple of pounds of air pressure to push liquid,so when beginning, make sure you are close to the tank with the ball valve cut-off so the pressure can be watched. Another way would be to disconnect all lines, (which you have to do anyway to prevent backflow, and hook an air linesto a fuel line and blow it out through a hose going to the fuel tank. Does your boat have electric fuel pumps, (like a bilge pump) on the tanks? All you would have to do is disconnect the line at the engine, and put the hose in a drum and turn the pumps on to empty the tanks. FYI, we're having the same problem with bio-diesel, fill the big rigs, and within 20 miles, it knocks all the sludge loose and plugs the fuel filters and shuts the trucks down, a real pain in the arse.

08-12-2008, 12:50 PM
did ya do the old stick it in your mouth ans suck suction? Done it plenty of times as a kid , the thought now makes me want to puke thou. Was wondering if I could hook a hose to the fuel pump and just crank the motor.

I really don't remember for that particular event, but I had done the start-by-sucking routine many times in my life, and I'm still around. Not too pleasant though, and I doubt if I would ever do it again, since you can buy a hand-squeeze siphon pump today in an auto-parts store or from Harbor Freight for less than 10 bucks. Or try using the fuel pump as you mentioned. It probably will work.

AI Inc
08-12-2008, 05:34 PM
Ended up sticking a shop vac with those attatched to blow on it . Pushed it right out.

08-13-2008, 03:37 AM
A.I., Great thinking, was listening to Click and Clack,(the tappet brothers on PBS), Saturday and a Coastie Machine Engineneer on a boat had a broken water jacket on an engine and did the same thing you did,way to go!

08-13-2008, 06:30 PM
I have recently purchased an old boat too, a 78 Bayliner 3050. We had about 50 gals of fuel to get out. I went to the Auto Zone and purchased an electric fuel pump that had hose barbs on either side ( i am not sure what vehicle it was from ). We hooked it up to a battery and pumped it all out. It beats the crap out of a mouthful of fuel.

08-14-2008, 04:13 AM
They make siphon kits that work quite well. I just used on on a piece of equipment that I let sit for 3 years with gas in it :hammerhead:

I got mine at a auto parts store. It cost me 8 bucks. Looks just like this.

08-14-2008, 05:01 AM
Yeah the syphon kits come with a bulb, that's what I use.

Thou I will say...
They work great until you use them every day,
then the bulbs act so stupid and besides it's so
inconvenient I just use my mouth and suck.

The good thing is with the clear tubing I can see the fuel
long before it gets in my mouth, maybe twice in 3 years
have I gotten a little.

08-14-2008, 07:06 AM
Just a word of caution, it can be very dangerous to pressurize containers with flammable liquid in them with compressed air.

Where I work if you are caught doing that you would be terminated on the spot.

The air can cause a static spark that could ignite the fuel with the proper air/fuel mixture.

Just something to think about.

08-14-2008, 07:35 AM
I don't think a shopvac is quite capable of really "pressurizing" anything more than a few PSI... and the compressor trick is using the outgoing air from the compressor hose to create a venturi vaccum effect on the fuel line thus creating suction. so you are not pressurizing the fuel tank.

08-14-2008, 11:45 AM
What causes the static is the friction between the air and the conductor (pipe/hose) or liquid I believe, not so much as high pressure.

I donít have the data with me at this time but I will find it if needed.

I work with a lot of flammable liquids and my company actually monitors the amount of LELís/LFLís (Lower explosion limits/lower flammable limits) in there machines.

Get the right fuel/air mix then add a source of ignition, a lot of people could be hurt or worse.

Iím not blowing smoke about this, you may get by with it a 100 times but itís that 1 time that can change your life or end it.

You donít have to believe me but at least research it for your self to be on the safe side. Or I can find the data and get back to you. I am almost positive read it on some OSHA literature.

Our company has us do so much safety training its hard to remember when and where I read it. Old age I guess.

Take care!

08-14-2008, 12:14 PM
I just read that the fuel is the cause of the static when moving though the lines not the air. My bad but when you add the air thatís when you may create the proper air fuel mix.

Here is a link with some insight.


Look under; What are safe practices for handling recovered flammable liquids, especially JP-4 and JP-8?

take care