Help with 9.9 Mercury stalling [SOLVED] Asked by Larry B. In Wisconsin I just bought a 1999 Mercury 9.9 four stroke outboard. It stalled a couple times. Will Sea Foam work for that?
Hi Larry. Smaller outboard engine stalling is typically caused by varnish in the carburetor circuits, slowing the rate of fuel to the engine. You can add a full can of Sea Foam Motor Treatment or Marine PRO in the fuel and let it run for a bit. The treatment will easily liquefy the varnish. When cleaning, adding more Sea Foam or Marine PRO to a smaller amount of fuel will work better and faster (because the cleaning concentration is greater). Keep in mind that it works when the engine is running and pulling the cleaning mixture through the carburetor, so it will take several minutes of running for the mixture to work through the fuel line. Should expect more improvement the more you run the engine. Hope this helps!