Flooding carbs and STP?

I get excessive white smoke at startup. It dissappears after a while. The engine also have tendencies of fouling plugs after 5-10 minutes operation at 3000 rpm. Even though I mount brand new plugs it fouls.<br /><br />I think some of my 8 carbs may flood. Its a 89 Evinrude 300 xp.<br /><br />Also the milage is lousy.<br /><br />The previous owner rebuilded the carbs but i wonder if there may be deposits in the float seat or something.<br /><br />My questions are these:<br />1. Could the carbs be flooding from my description? Of 8 plugs 4 looks fine, 3 looks oily and the last is totally solked with oil.<br />2. If flooading carbs do I have to demount them all. I am thinking of trying STP Complete Fuel System Cleaner. The previous owner claims the new gaskets can handle that kind of solvent.<br /><br />Greatful for advise!

Re: Flooding carbs and STP?

I'm not a fan of additives in 2-strokes. Interferes with the oil. Best to check those carbs from the inside out. Make sure the float levels are right and that the float valves are good. Check to see if you're getting good spark on all 8 first. You could have a torn fuel pump diaphragm, that would dump a lot of fuel into one cylinder.

Re: Flooding carbs and STP?

Thanks,<br /><br />Can you please expand on the fuel pump theory. Is there a separate fuel pump per carb/cylinder?

Re: Flooding carbs and STP?

Knowing little or nothing about the carbs in an 88 Evinrude V8, is there a level adjustment screw for the floats like in the Holley carb? <br /><br />Perhaps thats were my problem lies?

Re: Flooding carbs and STP?

I would expect that motor to have more than one fuel pump, like two. Follow the fuel lines and you'll find them. They are driven from pulsing crankcase pressure and if a diaphragm tears, that could leak raw gas into the cylinder that is providing the pulse.<br /><br />The carbs are quite simple in design. To adjust the floats, you have to take them apart and bend the float arm to achieve the correct float level.