Fuel Water Separator

acousticmark

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Oct 25, 2024
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Just installed Fuel water separator to my bass boat 90 hp Mercury, due to water in the gas. Finished install and primed the ball till firm. Came out a couple hours later to check the clear plastic water collection bowl and it was completely full. Is that normal? I wouldn't think it would have had that much water in the fuel. I emptied the contents of the resivour into a glass container to see if there's any further water/gas separation. It smells strongly of gas. I'm Leaving it overnight and will check in morning. Thanks!
 

dingbat

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Nov 20, 2001
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16,038
Just installed Fuel water separator to my bass boat 90 hp Mercury, due to water in the gas. Finished install and primed the ball till firm. Came out a couple hours later to check the clear plastic water collection bowl and it was completely full. Is that normal? I wouldn't think it would have had that much water in the fuel. I emptied the contents of the resivour into a glass container to see if there's any further water/gas separation. It smells strongly of gas. I'm Leaving it overnight and will check in morning. Thanks!
In operation, the clear bowl is full of fuel.

Any water will separate and fall to the bottom of the bowl to be drained
 

Buster53

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Jun 16, 2022
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Water and gas separate pretty much immediately. No need to wait overnight, but if it has a slight amber color and smells strongly of gas, sounds like it is gas.
 

Chris1956

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Mar 25, 2004
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You might want to siphon several gallons of fuel from the bottom of the fuel tank, into a Jerry can. Let that sit a bit and then siphon the bottom of the Jerry can into a clear container and see if you can get all the water out at one time. Toss some 2 cycle oil into the fuel to color the gasoline. The water will not be colored, making to easier to see.
 

Buster53

Petty Officer 3rd Class
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Jun 16, 2022
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A few years ago, I had some fuel/water issues and had a professional fuel polisher come to the boat to take care of it. When he pumped fuel into a clear container, the line between fuel and water was obvious, very distinct and immediate. There was no question. We could even look thru the opening where we pulled the fuel level sending unit and we could clearly see water in the bottom of the tank and that was using a flashlight to see into the tank. No need to add oil to the tank to darken the gas.
 

acousticmark

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Oct 25, 2024
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Thanks for the answers. The photo shows on the left the dark gas is from after the fuel water separator the right is light colored very cloudy with varnishy substance settled on the bottom that came from the clear glass bowl at the bottom of the fw separator. I assume it's doing its job. My question is why is the left so dark? I'm going to drain the tank and fill with new gas just to be safe. Hopefully that will help with the rough idling.
 

Chris1956

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Mar 25, 2004
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Gee, I do not like the look of either sample. Does the dark gas smell fresh? It looks to be quite old.
 

dingbat

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Nov 20, 2001
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16,038
Cloudy gas is often a sign of fuel separation. Not good.
“Cloudy” gas has not separated....otherwise it wouldn’t be cloudy and you would see three distinct layers on the bottom of the glass

E10 can carry up to 0.05% water by volume before separation and still be a perfectly viable fuel. In my area, your fuel can look like that in a week or two in the summer.
 
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