My mercury has a miss at idle when it's first started. After running it for about 2-3 minutes at WOT across the lake it runs fine until you let it set and cool off again. I mean it has to set at least 3-4 hours before it will start missing again at idle. Once it's warmed up it runs like a brand new one. It did this two years ago and I replaced the points and it was fine until last spring when it started again. I've checked the points and there still adjusted right . I don't think it's the carb. it just sounds like it's in the fire. Do coils cause these symptoms? Could there be moisture getting in one of the coils?