Draining gas tank

I have a 1990 Mercruiser 4.3l Alpha one Gen II in a Larson Laser. I need to drain the gas tank because of water in the tank. Tried to siphon from fill spout, no luck -removed fuel line at pump, nothing at all. Gauge on dash shows half to two thirds full. Unsure if we have a electronic fuel sending unit. Help.

Re: Draining gas tank

Howdy,


If you think you have water in the tank, you'll need to expose the top of the tank where the fuel gage sender is.

raise the bow enough to ensure that the water in the tank will be somewhere near the back of the tank (if the sender is near the back)

Remove the sender and use the siphon hose to "vacuum' out all the fuel, water and other debris (if any)

Use clear hose with a piece of plastic (PVC) pipe clamped on each end so you can move it around in the tank and your helper can easily switch from full containers to empty ones. Use a hose long enough hose to make it easy and maybe put a ball valve on the other end so the helper can shut it off when switching containers.

Do it outside away from the house,garage etc. and have a fire extinguisher handy.

Plan on removing the fuel pickup line, screen and anti-siphon valve (if installed) so you can inspect/replace as required.


Cheers,


Rick

Re: Draining gas tank

I just went through this earlier this week.

Do you have access to the tank? If so, remove the sending unit, and you can siphon from there. I had to do that, and was even able to 'aim' the hose to the very back of the tank. I figure I got about 99.5% of the fuel out.

If you don't have access to the tank (without cutting the floor open), you can tap into the fuel line where it makes its first connection (fuel/water separator in my case), and hook up an electric fuel siphoning pump to the line, and get it out that way.

If you have a primer bulb, disconnect it at the discharge side, connect another line to it, and you can pump itout that way. This will take the longest amount of time and pumping, but it will work.

If you don't have a primer bulb, now might be a great time to add one.

BTW, how did you confirm water in the tank?

HT32BSX115 types faster then me.

Re: Draining gas tank

Welcome to iboats!

You should be able to attach a fuel line to the fitting on the top of the tank and either use siphon action (a primer bulb usually used for outboards would be ideal to start the siphon) holding the end of the fuel line below the level of the tank, or hook up an electric fuel pump to do the job. Be VERY careful not to create any sparks when using the latter option.

Re: Draining gas tank

3 solutions in 3 minutes. Ain't iBoats great!

Re: Draining gas tank

What do you do with all the bad fuel??

Re: Draining gas tank

In my case, I took 41 gallons to my local landfill. The take hazardous materials at no cost. After the first trip with my lowly 5gal can, the guy gave me 8 more cans to borrow. Sweet! I did put about 3 gals in one of our vehicles. Ran fine, but I really don't recommend doing that.

Re: Draining gas tank

If your watered gas is not soured (smells like lacquer thinner) you can put it through some fine filters such as paint filters and you can separate out the water with, drumroll please, a fuel water separator. In fact if the fuel only has water in it you can run all of it through a drainable type fuel water separating device. Once you have it clean you can put it in the boat, or your lawnmower, or your brother in laws car. or you mother in laws Harley. The possibilities are endless! If that's too daunting it can be disposed of properly. Just get the fuel tank completely clean inside, and install a fuel water separator filter if the boat doesn't already have one.

Re: Draining gas tank

Confirmed water in gas by pulling fuel from gas line by turning the key to let it pump it out in short spurts. Let it set and seperate. We have not one but two floors to go through in the boat since someone had replaced the original floor by going right over it. If we do get to the tank, what do you clean it with after it is empty?
Thanks so much, this is so helpful!

Re: Draining gas tank

Since it's only water and you don't suspect debris (yet?), I'd recommend just sucking out the fuel to some remote jugs for separation and inspection. If it's only water you could separate it out and reuse it. But since water is in there you need to prevent it from happening again. Check your vent system (if present) and filler for good hoses and fixtures. If the fuel isn't full of debris you may not need to go through the floor to the tank top. If it smells like lacquer and it has no junk in it just recycle it.
If it's dirty and watery and old you need to junk the fuel properly. Then you need to access the tank. Since you were able to get fuel with the on board pump I'm thinking fuel injected engine. They have good strong pumps, you could use the pump to empty the tank, but it takes fooling the engine control manager (ECM) because once the engine goes through a timed and sensored sequence the ECM will shut off the fuel pump.
Also the pump could have a strainer over it's intake so you wouldn't be sure that the fuel is debris free. If it pumps strongly and consistently just use it. If it clogs up and stops pumping but can still be heard running you are going to need to get into the tank. If it does that turn it off, running it dry will break it, no sense ruining a good pump.