What causes gel in an outboard carburetor? [SOLVED]

I have a 1991 two-stroke outboard with a carburetor. It was running poorly so I tried replacing the fuel filter. That didn’t help so my mechanic pulled the carburetor and found the bowl full of a clear gel. My mechanic thought it might be caused by some reaction in the fuel but wasn’t sure, then tried to soak it in Sea Foam…That didn’t work so he ended up brushing it out. Do you have any ideas what caused the gelling in the carburetor? Would using Sea Foam Marine PRO prevent the problem?

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Jim D.
Jim D.
4 years ago

Great question Ronald. What you discovered is what can happen when ethanol is used in older carburetors. The gel substance in the carburetor is the corrosive reaction between carburetor parts made from aluminum (alloy, pot metal), ethyl alcohol, water and electricity. The gel dries quick to leave a white powdery crust of corroded aluminum. Aluminum corrosion is typically found in carburetors that pre-date ethanol gasolines coming on the scene (2003 or older engines is a common rule of thumb). Remember that Sea Foam Marine PRO in fuel is always working as a fuel system lubricant and to treat carburetors, intakes and cylinder cavities (Sea Foam Spray) with when storing seasonal engines. And, avoid leaving ethanol in any older fuel system. [Newer than 2003 is typically more ethanol-proof.]