I am hoping you can help me. I have a 2004 MC 197 with a GM Vortec TBI. When it is warmed up and idling in between ski sets it "stumbles" every once in a while. It almost stalls. It seems to run fine otherwise although I do notice some unburned gas in the water sometimes when it starts (hot). I have changed all the ususal tune up parts, had it on the Scanner (no codes), checked the Engine Temp. Sensor, run lots of Fuel injection cleaner, etc. I'm suspecting the Engine Temp. Sensor is faulty sending a bad reading to the ECM intermittently. Any ideas?