Who's our resident outboard motor guy?

What it's doing, it will rin at 2000-2500 rpm all day long and not miss a beat. But open it up from there and after 10-15 minutes it starts popping, farting, misfiring and an alarm sounds which I couldn't determine what was causing it to alarm, what was wired to that.
Let it sit 10-15 minutes and fire it up and takes right off, runs great. If kept below about 2750 rpm it won't act up at all. But once it does while running higher speed then it starts it's fit at any rpm.
Wait til you can turn the key on and not have the alarm and all is good again. If not taken above 2750 it will run happily for hours. As soon as it's taken above that the trouble starts and once it does sometimes I can cut it down below 2750 and stay running just fine/ other times if it's had it's fits, gotta wait for it to cool down before it will run at all . I'm pretty sure it's electrical not fuel related.
The VRO is bypassed, gas + oil is mixed manually like any older outboard. Fuel pump is pretty new.
Those plugs that were in it when we got to the lake were brand new and the bottom one fouled out within 1/2 a tank of fuel.(about 6-7 gallons worth of run time) the boats owner and my son went to town that night and found plugs for it at the o'wrongleys.
They didn't have champions so they got ngk's.
We installed them and took it out and ran it at all speeds for around 15 minutes and it ran great. Thought we had it fixed. Yesterday we were out with it damneer all day and I was out back riding on a tube and it raised it's fits after about 20 minutes of 3/4 to full throttle. I pulled myself up to the boat by hand over hand pulling on the tow rope and pulled the new plugs out while I was sitting in the tube, in 30 feet deep water. They looked fine, none fouled. My son's father in law (boat's owner) bought all the plugs that o'wrongleys had in stock which was 4 qty.

We put all 3 in on shore the night before and put it in for the above mentioned test run.
But, in 30'of water and it acted up again, I was expecting to find that bottom plug fouled again, he was on the boat, ready to hand me that 4th plug to thread in. I didn't since it wasn't fouled out at the time.
In the time I spent pulling out the plugs in the water, eyeballing them, putting them back in, and the engine cover back on, we were able to fire it right up and it ran great again/ again for ~15-20 minutes.
Every other time besides that time I pulled the plugs on it in the water we had to sit 15-20 minutes for (whatever) to cool so it wouldn't alarm as soon as key was switched to "run". Seems like that time it acted up and I pulled the plugs it was a shorter wait til it would cooperate again.

My thoughts were the coil which fired that cylinder that initially fouled out being bad, and I was wanting to replace "that" coil first.