engine icon flashing on smart craft guage

[steam1]

I have a 2005 optimax 225 with 170 hrs and the engine icon on the smart craft started flashing. The motor runs rough at idle and seems to be a miss,and smoothes out as soon as throttle is raised. I pulled the plugs and the # 3 looks as clean as it was when I put it in,almost new
Anyone have this problem and what is the solution.looks like this plug is not fireing at all