My neighbor has a 1999 25hp 2-stroke, 2 cylinder twin carb Yamaha on a pontoon. It starts easy runs smooth till you bring it all the way down to low idle. It will run without dying for 2 or 3 minutes then cough once and kill. I pulled the carbs and cleaned out some black tar looking stuff from the bowls, removed the jets and sprayed those. Put her all back together and the same results. Replaced the fuel line, tank and gas. Still the same. Tried setting the rich/lean screws richer and leaner, still one cough and dies...any ideas what else could cause this???
