Reply To: 1958 envinrude 35 HP big twin running rough

[fisherman6]

If you are using ethanol-blended unleaded your carburetor may be worth a look. You state that you put a new kit in your carburetor. Did that kit include a float? I know even the new OEM kits still have a cork float in them. They are a lighter color and are supposed to be coated with an ethanol resistant coating but I have not tested this. I only run ethanol-free gasoline in my outboards. If you did not replace the float and it still has the shellac coating, the ethanol will dissolve the coating and it will end up in the bottom of your carburetor’s float bowl in little gummy bits and block fuel flow. It takes a little time for this to happen, but if the carburetor is not run dry each time and the float is floating in fuel all the time, it will happen. Marine Sta-Bil has the ethanol additive in it too, but I’m not convinced that will save a shellac coated cork float from the effects of the ethanol. I’m not sure what the Sta-Bil does chemically, but it does not magically make the alcohol disappear.
-Ben

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