I have a 9.9 johnson. It starts and runs fine but stalls after about 20-30 sec. It will start right back up. It will run with the choke on but not at an idle. IT always ran good before. I was wondering if I have the fuel mixed to rich. I mixed it 50:1 like the book says. But may have mixed it a little richer the last time because I got in a hurry and couldnt find the measuring cup. It does smoke a little.