Ignition Woes! 1977 200 Horse Johnson

Hey all!
I gave my Wellcraft to my brother so it would at least stay in the family instead of selling it. And lucky me I got to work on it today during my vacation. I was trying to get the 1977 200HP Johnson V6 outboard running as smooth as when I had it.

Here are the symptoms. It starts up fine. I have it timed at 5 BTDC at idle and 28 BTDC at Full throttle. When it hits full advance, about mid throttle the port side coils stop firing. Is this a power pack problem or the stator and timer base? Unfortunately, I don't have all the fancy tools and testers that the book calls for. Just a timing light. I didn't check the color of the spark. I just know that the timing light works and then stops working on the port side cylinders when I get near full throttle.

Thanks,
Buenos