25hp Mercury outboard missing on top cylinder

[Ssimmons]

I have a 25hp Mercury that won't fire on top cylinder when first started. After about 3-5 minutes it will start spitting for about another 30 second and then the cylinder starts working fine. I can cut it off all day and restart with no problems but if it sits a day or two it starts the same thing all over again. Where do I start at to fix this problem?

[FRANKGLOCK]

change plug plug wire change coil to other side and see if works