miss firing at idle

I have a yamaha 2003 F25eshb that miss fires at an idle when you start it up runs fine then starts miss firing. I checked carb and fuel pump everything seems fine it had been running fine was on the water turned it off and when it was restarted it was missing above an idle runs fine any ideas ???

[boats.net]

Sometimes they will run rough when you first start up cold then when warms up runs ok.