My motor will not idle the last few times I have run it. It starts fine and will idle for about 20 seconds, then die. I can start it back up with no problems and once I quickly push the throttle to get the rpm's up a little bit, the motor runs just fine. When I go back down to very low rpm's or idling, the motor stalls out. I replaced the spark plugs when this came up and have always winterized it with fuel stabilizer, fresh oil, etc. I recently put a cleaner in my gas and have run the boat at about 2200 rpm's for 30 minutes, but that doesn't seem to have helped. Any ideas of what I can try?