Yamaha 2hp idles rough and misfires

[kjlgpw]

I own a 2003 Yamaha 2hp that starts easily and runs fine at higher speeds but runs rough and misfires at throttle settings lower than the start position of the throttle lever. The carburetor has been disassembled/checked twice and seems to be in good shape. How smoothly should this engine run at idle and just above idle?

[boats.net]

They are not as smooth as the 2 and 3 cylinder engines. They shake a little at idle.