interpretation of fuel sample result

Good afternoon. A little help with a water-in-fuel issue... Running a new-ish 115 hp Suzi. This has happened to me twice; I drew a fuel sample (10% ethynol gasoline from Navy Exchange) into a clean pickle jar, closed the lid, and determined the fuel sample was normal... clear and bright, slightly amber. After letting the fuel sample sit in the closed jar for a time, no change. When I open the jar and let it sit for a short time, the sample turns cloudy and a bob-let of dirty water emulsifies (if that is the right term) at the bottom of the jar. Am I looking at a fuel sample that i initially misinterpreted? or am I looking at a sample in which water absorbed by ethynol became visible? Is there a difference? Either way there is water in the fuel.... right?

That sounds like ethanol separation due to water. It's possible that it's already partially saturated, so it's not taking much additional moisture before it starts to separate. Generally ethanol gasoline mixtures will burn fine with a little water in them, but once there's too much water you get separation and the fuel becomes junk.

I know older outboards are not designed to run ethanol (seals, o-rings, etc.) but what about the new outboards? Also, I know ethanol absorbs water, so not a good idea if the fuel is sitting for a length of time. What time frame was the above experiment? Also, leaving ethanol over the winter can cause a yellowish varnish to foul the carburetor-from first hand experience. I would avoid the ethanol if possible. Does anyone have experience with an additive that can counter the ethanol? I know it's hard to find non-ethanol gas at times.

Phase separation looks milky, not dirty.

My brand new Mercury manual says ethanol is OK but non-ethanol is even better. To me that is saying ethanol is fine...but one more thing they can complain about if a warranty issue goes sideways....especially if you don't burn that fuel up regularly.

I would need a picture to better evaluate.

psneeld said:

Phase separation looks milky, not dirty.

My brand new Mercury manual says ethanol is OK but non-ethanol is even better. To me that is saying ethanol is fine...but one more thing they can complain about if a warranty issue goes sideways....especially if you don't burn that fuel up regularly.

I would need a picture to better evaluate.

Click to expand...

You sailed on Polar Star? Boutwell, Northland, Sherman here.

I've been running gas station 10% ethynol since new. I got water past my Racor becuz I let the fuel lines get too old... a section had been sitting in dirty water since 2017 (in the Boston Whaler tunnel). I drained or replaced everything from primary back to tank... fuel lines, Racor and primary, drained the VST. The Vapor Separator tank DID have water in it. Problem not solved. Pulled VST tank and found interior components and tank in pristine condition. no rust or debris. Re-assebled will test tomorrow. Since I didnt really change anything, I expect I'll continue to troubleshoot fuel injectors/rail.
BREAK. Time frame on fuel sample becoming cloudy was a week the first time and a few minutes the second, but both times the fuel looked great until I removed the lid from the jar. Upon removing the lid, cloudy is exactly what happened pretty quickly... then the boblet of water formed, the water looks dirty, it is much more amber than the fuel... looks like varnished fuel but it's water cuz it hugs the bottom. After the water boblet forms, the rest of the sample goes back to clear and bright.