old mixed gas

[jrjr12]

I recently bought a 77 sylvan 17' boat for a project boat.
The boat has a built in 13 gallon gas tank that looks pretty old. Previous owner said that he filled the gas tank with mixed gas for a 2 stroke before his lower end unit cracked this past fall. I have a newer 2 stroke evinrude that I plan on swapping out with the existing one on the boat. I am worried about the gas that is currently in the tank. Previous owner said that he used non ethanol gas which is good, but I do not know if he put any stabil in at the end of the season.
My question is, to prevent damaging my good motor with potentially bad gas, should I add some stabil or dry gas into the tank?
Or should I drain the gas out into a few external gas cans and then run the gas through a funnel with a gas filter built in (not sure if I can even do this with the gas being mixed with oil)?
I am leaning towards draining the gas from the tank and trying to figure out a way to clean the inside of the gas tank just in case there is any debris in the tank to try and do preventative maintenance.

I may be overthinking this whole thing, but I would like to do whatever I can before the season starts to know that I will be in good shape for this upcoming season. Thanks in advance!

 

[CedarRiverScooter]

If it is non- eth, the gas should still be OK. If you aren't going to use it in the next month, add some stabil. If you are going to clean out the tank anyway, might as well siphon it out & use it in your car, maybe mix 50/50 with straight gas.

 

[turbotodd]

The whole "non ethanol" being better--is a total myth. Most don't know this but the government doesn't mandate fuel be labeled with the sticker "up to 10% ethanol" unless it's 7% ethanol content to 10%. Below that it's anyone's guess. Supposed to be 4% or lower to be labeled "no ethanol" but I am sure it's not enforced much; or I haven't seen proof of it. Some gas stations get their supply from a gas truck. Others get it from a pipeline underground. The same pipe that carries gas also carried diesel and E85 or whatever else they have. Also some pumps use one pump to move fuel from underground to your tank, so there is sometimes some residual leftover that pumps right into your tank. So Point being, you really do not know what you're getting unless you test it. I have some ethanol test strips at work that I use often and those that say that they filled with "no ethanol" will show 5% sometimes more. I've seen it 12-15% sometimes.

Ethanol doesn't cause the problems as long as it's formulated correctly and accurately. It's the fuel blend in general not "just" the ethanol.

If he put 13 gal in 6 months ago, I'd bet there's maybe 9 left. The rest likely disappeared into thin air (evaporated)-and similar to saltwater, when it evaporates, it leaves the GARBAGE behind, and there's where the problems come in.

You can't pour new gas on top of old gas and expect to make it new again. That doesn't work. Similarly, you can't pour stabil (or any other fuel "treatment") into old gas and expect it to be new again. The only way you're going to get new gas is to remove all of the old and put new (fresh) fuel in. Similarly, you're not going to take a carburetor that has been filled and plugged with staled fuel and put new gas in it, and expect it to run again. Think about it. You can put any chemical you want in there but if the passageways are clogged, they won't unclog unless you can get SOME cleaner through it which "might" (rarely) allow the cleaners to dissolve it. You would be surprised how many powerheads I've had to replace due to a plugged jet. I mean if it ain't running right, back off the throttle and find out why. Or keep running it until it melts a piston. I don't care either way, in fact we are slow at the shop, go ahead and run them plugged all they want. Just kidding...Id' rather folks take care of their stuff than have to work on them all day.

Most modern engines since about 2004-ish are rated to use up to E-10. Most modern carburetor parts and fuel pump parts and tanks and hoses are rated to be used with E-10 as well. About 2 weeks is all you will get out of summer blended fuel before it starts running funny. Winter blended fuel maybe a month tops. It's blended differently summer to winter, because summer fuel doesn't sit in the tank very long because people are always on the go. Winter blended fuel is formulated to sit a little bit longer yet still fire the engine off quickly when it's cold outside. Sometimes different parts of the country have their own blends as well based on overall climate. There's a whole lot more to gasoline than most think....I know some of it but there's even more that I do NOT know, and may never.

 

[KMixson]

Turbotodd, You are correct. I used to deliver gas to stations by tanker. One thing that heard people say a lot is that one brand was better than another brand. They do not know that it all came from the same place. Exxon, Shell, Amoco, Hess and any others trucks would load at the same terminal getting the same gas.Even if it was a different terminal it may be coming from the same pipeline. You will notice the terminals will be close together in areas. The pipeline tells them when to open and close the valve for that particular product as that slug of fuel passes by. The different fuels are pumped through the same pipeline.

 

[Pappy]

Correct......
YOU CANNOT BRING BACK OLD GAS BY POURING STABILIZER IN IT...............PERIOD!
Do not worry about the few gallons of gas left in the tank when you have a valuable piece of machinery you are about to subject that fuel to that you can very likely damage as a result.
KMixon - also correct! Not sure if you are aware of this but they used to put "pigs" in the pipeline to help separate the different fuels running in the same pipeline. Not any more. A pig was a separator similar to a drum. Now the only time a pig is used is for internal pipeline inspection.

 

[MrGiggles]

Gas is cheap, outboard rebuilds aren't.

If in doubt, siphon and replace.

 

[jrjr12]

Thanks for the replies, I am going to pump the old gas out and start fresh in the spring. Does anyone have any suggestions on how I should try and clean the inside of the tank to ensure that there is no debris or sediment inside?

 

[1960 yellowboat]

Thanks for the replies, I am going to pump the old gas out and start fresh in the spring. Does anyone have any suggestions on how I should try and clean the inside of the tank to ensure that there is no debris or sediment inside?

The only way I know is to take the tank out, put a little gas in it, slosh it around, and dump it out.

 

[CedarRiverScooter]

After you remove tank & pour out old gas, I would wash it out with hot soapy water - mainly for safety. Obviously get all the water dried out. Then you can use a flashlight to observe the interior surface, could be rusty. There are sealers you can use to mitigate this. Good luck.