Bad Gas/Petrol In Tanks

[Chotu]

I have about 15-20 gallons of very old gasoline/petrol in my tanks.

I have 3x50 gallon tanks. 2 tanks have 5 gallons each in the bottom, one tank has about 10 gallons.

This gasoline is non-ethanol, treated with stabil fuel treatment, but it’s what?..... 4 years old now? With vent tubes exposed to the Florida humidity and temperature cycling.

There are no drainage pickups at the bottom of the tanks. There are only pick ups from the top with “straws” that pull most (but not all) of the fuel out.

By memory, I think there was a small access hole at the top too. Enough to awkwardly touch half of the bottom with a rag on a stick.

It’s time to bring the fuel system back to life.

What’s the best way to proceed?

[rslifkin]

If it still looks like gas and smells mostly like gas, I'd just confirm there's no water in the tanks, top off with fresh fuel and go for it. I've burned 2 year old stabilized gas from a sealed container with no issues. Longest I've gone with stabilized gas in the vented boat tanks is probably 10 months or so, both with E10 and E0 (boat gets stored for winter with full tanks).

[DefinitelyMe]

If it were me:

I'd be more concerned about water in the fuel from condensation inside the mostly-empty tanks than the fuel itself being bad. Non-ethanol, treated fuel sitting for four years isn't that bad. I'd just fill up with new fuel, make sure there's a good water separator in the fuel system and go for it.

If you're worried, take a sample out of the tank. If it's light-coloured and smells like fuel, it's good. If it's darker yellow and smells like varnish it's not so good.

[Chotu]

I should add:

Main engines are fuel injected. But gearing up to run the generators and air conditioning soon.

[Chotu]

Ok. I think I’ll start with the sample. That’s not a bad way to go.

I do have a single Racor filter/separator in the system.

[rslifkin]

As a thought, fuel does lose some octane over time, even when stabilized. So if the stuff seems at least half decent, plan to use higher octane than otherwise required to fill the tanks. That should give a resulting mix good enough for everything to be happy, especially considering the worst of the tanks will only have 20% old fuel in it.

[Chotu]

Originally Posted by rslifkin

As a thought, fuel does lose some octane over time, even when stabilized. So if the stuff seems at least half decent, plan to use higher octane than otherwise required to fill the tanks. That should give a resulting mix good enough for everything to be happy, especially considering the worst of the tanks will only have 20% old fuel in it.

Ok. I’ve done this before. Just topped off with fresh and run it through. It was never this old though. I’ll use the highest octane I can get.

I’m will pull the sample and watch the Racor system.

And probably run it through the generators, which have carbs I can clean in case of problems.

The first tank of gas I ever got in this boat was all water. The day she was launched. It destroyed my fuel injectors and cost a fortune. The fuel company didn’t take responsibility for that.

So I’m a little nervous of running any fuel at all through the outboards unless it’s perfect.

[NorthCoastJoe]

I would suck it all out and check the tanks for crud. You can buy a small 12-volt fuel pump on Amazon for $20 that you can use to transfer the gas to jugs and filter it through the Racor. It a bit of work but at least you would know your tanks are clean.

When I first got my Pearson 30 it had an Atomic-4 engine and the gas was nasty with crud, so much so I pulled the tank to clean it. Bad "O" ring in the fuel fill let rain in. I am diesel now with a very clean fuel tank.

[Scubaseas]

Originally Posted by DefinitelyMe

If it were me:

I'd be more concerned about water in the fuel from condensation inside the mostly-empty tanks than the fuel itself being bad. Non-ethanol, treated fuel sitting for four years isn't that bad. I'd just fill up with new fuel, make sure there's a good water separator in the fuel system and go for it.

If you're worried, take a sample out of the tank. If it's light-coloured and smells like fuel, it's good. If it's darker yellow and smells like varnish it's not so good.

X2, Good advice. If it smells like varnish do not run it through an injector. Carb maybe if you are willing to rebuild it. The varnish gets on the valve stems and can seize the valve open which can then sometimes go right through the top of the piston. I've seen this on people running engines on 5 or even more years old gas. If you are going to run it put some SeaFoam fuel additive in the tanks. If you want to boost the octane use some Avgas or octane booster.

[Chotu]

Originally Posted by NorthCoastJoe

I would suck it all out and check the tanks for crud. You can buy a small 12-volt fuel pump on Amazon for $20 that you can use to transfer the gas to jugs and filter it through the Racor. It a bit of work but at least you would know your tanks are clean.

When I first got my Pearson 30 it had an Atomic-4 engine and the gas was nasty with crud, so much so I pulled the tank to clean it. Bad "O" ring in the fuel fill let rain in. I am diesel now with a very clean fuel tank.

Mentioned in the first post, you cannot suck it all out.

This is of great concern because if there is water in the bottom, it’s going to get stirred up and sucked out when things are rough. That’s exactly when that happens.

[rslifkin]

Originally Posted by Chotu

Mentioned in the first post, you cannot suck it all out.

If you can find a way to shove a tube into the tank (either down the fill hose, or through a hole left by removing a sender) you could get the tanks pretty close to empty. Certainly closer than using the existing dip tubes. But until you sample what's in there, you won't know if it's worth trying to drain them anyway.

[Chotu]

Originally Posted by Scubaseas

X2, Good advice. If it smells like varnish do not run it through an injector. Carb maybe if you are willing to rebuild it. The varnish gets on the valve stems and can seize the valve open which can then sometimes go right through the top of the piston. I've seen this on people running engines on 5 or even more years old gas. If you are going to run it put some SeaFoam fuel additive in the tanks. If you want to boost the octane use some Avgas or octane booster.

I really don’t know what varnish smells like. I know what old gas smells like.

[Chotu]

Originally Posted by rslifkin

If you can find a way to shove a tube into the tank (either down the fill hose, or through a hole left by removing a sender) you could get the tanks pretty close to empty. Certainly closer than using the existing dip tubes. But until you sample what's in there, you won't know if it's worth trying to drain them anyway.

OK. That’s true. I had better get to work getting that sample.

So many pressing things to get done.

Luckily, the fuel system has a pump (that’s another issue) that I can use to pull some out the dip tubes.

[flyingfin]

You did not say what material the tank is made of, or where the fuel & water separator is located. Normally I would recommend you pull as much fuel out with a hand pump using the fuel pickup lines, then put new 10% ethanol fuel until you get each tank 1/3 full and go out under power on a rough day, make sure you get the tanks sloshing good - be prepared to change filters several times.
Ethanol is a wonderful cleaner - it will wash all the crud off the inside of your tank and put it in your filters so be prepared!

[Chotu]

Originally Posted by flyingfin

You did not say what material the tank is made of, or where the fuel & water separator is located. Normally I would recommend you pull as much fuel out with a hand pump using the fuel pickup lines, then put new 10% ethanol fuel until you get each tank 1/3 full and go out under power on a rough day, make sure you get the tanks sloshing good - be prepared to change filters several times.
Ethanol is a wonderful cleaner - it will wash all the crud off the inside of your tank and put it in your filters so be prepared!

Sorry. Here’s that information

Tanks are Moller polyethylene and show no signs of any crud in them. Water is my concern. Stale, unusable gas a secondary concern.

Racor filter/separator is located in a vented overboard “explosives locker” on the bridge deck.