I have a 1981 35hp Johnson. My problem is that it is only firing on one cylinder the top one. I have replaced both plugs and the bottom coil, and still no fire on second cyl. I can put throttle full power and I crawl across the water. Could it be my power pack or is it something else. Can a bad Power pack cause it to only fire on one cylinder. Im new to working on boat motors so any help is appreciated greatly. thanks all. 