I have a 1982 Johnson 70 that when I first start it #1 cylinder does not fire, only runs on 2 & 3. Usually if I let it run after a while (10-15 minutes) #1 will start to fire, intermittenly at first then eventually it runs okay. But I have had times when #1 won't fire all day? I have already replaced the power pack, rebuilt the carbs (I realize that has nothing to do with spark) and installed new plugs. Any reason the motor would have to "warm up" before #1 cyclinder will fire?