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RoadRacer 07-06-2010 11:11

Gas / Ethanol Fuel Separation ?

I spent three wonderful hours :banghead: working on my new 15-hp 4-stroke outboard this past weekend in 90+ deg heat. My daughters had to paddle the dingy back to the mother ship and I determined there was water in the carburetor throat. I disassembled and cleaned the Keihin BCM carb only to discover that the fuel tank was the source of the mess! It appears that either Gatorade was poured in my tank or that the gas & ethanol had separated! Has anyone had a similar problem and how are people handling the ethanol problems with marine engines? I havenít found an ethanol-free service station near Annapolis yet.


s/vfootloose 07-06-2010 11:35

I was down in the Fl keys last week and a lot of the marinas are selling non-ethanol gas expensive but cheaper than engine problems It was $4.00 a gal.

anjou 07-06-2010 12:02

Are we likely to get the same problems in europe? Are the chemical ingredients the same in our petrol?

Are you sure the two components can separate out or is it just a theory?

RoadRacer 07-06-2010 12:18

Good question Anjou! That is the reason I'm posting on the CF as there are bound to be great minds here thatíve already solved this!
When draining the fuel into numerous plastic water bottles, there were three distinct layers. Top yellowish Gatorade, middle water-clear liquid that I took to be alcohol by the feel and smell and on the bottom a chalky white layer.
The tank had about 2.5 gallons in it and I took out about 30+ ounces of the clear center-layer liquid! I still believe that something was put in the tank!
I donít know if ethanol will separate out from the hydrocarbon concoction that we call gasoline??


anjou 07-06-2010 12:33

Depending on the time taken to separate, it might be sufficient to shake the can every time you use it, but if its more rapid, it might actually need shaking as its being used.

We had problems last year with the outboard. The gas in the can had been stood for months. I connected the line, started the engine and ran it for maybe 10 mins before it splutterred to a halt. After a lot of pulling, it would fire and rev hard and by the time it got into gear it would die again.
It was a typical gas type problem. I kept pumping the primer bulb to keep pressure in the line but it didnt improve.

Next day I stripped the carb and found dirt in it but not enough to kill the engine. The vacuum pump membrane wasnt in a very good condition but I was over riding any deficiency that may have had by pumping the bulb, so that couldnt be the cause.

When I checked the gas can, i was sure I could see what looked like water rolling round in the bottom but I poured some out into a jar and it didnt look like water then.

All very suspicious. Maybe it was the dreaded ethanol?

I knew theres a good reason why I like diesel

S/V_Surya 07-06-2010 13:11

So I have Honda four stroke and had carburator problems a few years ago. After cleaning carbs I kept getting fuel filter clogs. I installed a "large prefilter" from the auto store. When it clogged I pulled it out and was getting this gel type material. When It dried it looked like fine dust. So now I carry a spare prefuel filter and only use high octane fuel in tank. So far so good but I admit I have not used it very much last year or even this year. So jury is still out on what it was or where it came from. But I would recommend a cheap prefilter that is easy to change.

Oh. and ethanol will not separate out into layers from the petrol.

cal40john 07-06-2010 13:30


Originally Posted by S/V_Surya (Post 465005)
Oh. and ethanol will not separate out into layers from the petrol.

I read somewhere that once the ethanol has absorbed enough water it can separate and will be a bottom layer. Don't remember where, so don't know how much validity to give to it.


TexSail 07-06-2010 13:34

My outboard mechanic told me that ethanol related problems were half of his business.

We have had very good luck with:

1) a spin on type fuel/water separator between the tank and the motor.
2) Use Sta-bil in the fuel.
3) Try to seek out ethanol free fuel but sometimes it is not available
4) Try to not keep fuel over the winter
5) Try to rotate your tanks so that the oldest gas gets used first

The ethanol water problem causes sputtering in a four stroke but can total out a two stroke.

anjou 07-06-2010 13:38

Does this mean the ethanol is hydroscorbic?

ie, it attracts water and binds to it, which makes it heavy causing it to separate?

TexSail 07-06-2010 14:01


Originally Posted by anjou (Post 465031)
Does this mean the ethanol is hydroscorbic?

ie, it attracts water and binds to it, which makes it heavy causing it to separate?

No chemist here, but I believe that is correct.

anjou 07-06-2010 14:06

Maybe thats what I saw in the bottom of the can and thought it to be water, but after shaking it up it may have risen and hidden within the rest of the fuel

ViribusUnitis 07-06-2010 14:55

Ethanol is hydrophilic. It just loves water, and everything that is water soluable is generaly soluable in ethanol. That includes every bit of crude in every tank between the time it was added to the gasoline, and the moment it gets to your engine. Ethanol also loves gasoline. It'll disolve and stay disoved in the gasoline, bringing all that crude, and water with it. Well, at least untill you add too much water and upset it's ability to stay disolved. Then some of the ethanol will be disolved in the water phase, and some will be disolved in the gasoline phase, and you don't even want to see the calculations to figure out how much is in each.

Ethanol won't seperate into layers with gasoline by itself. If it seperates into layers, something has probably added water to it, which would form layers anyway. If you add enough water to the gasoline, you'll remove enough of the ethanol to lower the octane rating of the fuel. Generaly, that's a bad thing, and good for destorying engines.

If you want to cope with ethanol in the gasoline, have fittings and tanks approved for use with ethanol, keep it dry, and keep it freash. Don't let the fuel sit, and make sure that moisture problem is under control.

osirissail 07-06-2010 19:43

I remember a few years back when some States mandated only ethanol gasoline could be sold and the marine boaters were suffering all sorts of problems with their engines including the dissolving of the FRG/plastic fuel tanks due to the alcohol in the fuel. Here are some links to warnings about using ethanol gasoline in outboard motors - -
Boat Engines - Dangers and Precautions Necessary with E10 Ethanol-Blend Gasoline.
ethanol fuel and outboards
Ethanol and Boat Motors Don’t Mix*|*Facts About Ethanol
and the best one - - Ethanol-gas blend can harm outboard motors | The Augusta Chronicle

- - Automobiles and other vehicles are having to switch back to metal fuel tanks from FRG/plastic as the ethanol gasoline is dissolving the FRG/plastic tanks. Not a good prospect for cruisers if you have FRG/plastic tanks and have to go back to steel tanks which means rust and other problems. From Practical Sailor article: Ethanol Fuel Attacks Outboard Engines, Inboard Engines and Fuel Tanks
"When used to store E10, these fiberglass tanks dissolve, literally. The alcohol, which is a solvent, begins to molecularly disassemble the fiberglass resin matrix"

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