Nissan 15hp misfire?

[seachicken]

I have a 2003 Nissan 15hp 4 stroke that has developed a problem that seems to be similar to a misfire. The motor will idol rough and when given throttle it seems to be running on one cylinder, then the other cylinder seems to spiratically kick in and everything will run fine until you idol back down, in which case the process will repeat its self. On occasion, the problem will go away after the motor has been running for a while (30 min or more). The carb has been taken apart and cleaned twice in the past month and everything seems to be fine with it, Im thinking it is an ignition problem, such as a coil pack. Any suggestions on where to start?

Thanks,

Ty