I would think your AFRs would be alittle rich in the heat and humidity of summer . Those wide bands are a good broad range tuning tool . But they still just average 4 cylinders together . If you've ever seen a dyno run with 8 O2s in the headers , The cylinders will be all over . Ive seen them as much as 2 full points apart. So if you have one at 11.0 and one at 13.0. Your single widebands are still saying 12. If your AFs drop below 11.0 your overrich from my experience. One fat cylinder can drop 50-75 hp.

Right I get that but it's all I got to go by, sure is easier then reading plugs! Lol

It would be interesting to take all plug readings now at 11.5 to 1 + or - and then get them up near high 12's to 1 and see if any rpm gains and repeat plug check. I've seen them range on the dyno as you mentioned especially with non flowed ported heads. Numbers seem to jump everywhere. CNC'd heads and port matching help a lot but again need help here and there to achieve consistency. But even in a perfect world their will always be some fluctuation. Being confident while pinned for miles on end is a good feeling.

In a nutshell wideband is an awesome tuning tool as you mentioned while plug checks tell the tale. That's where staggered jetting can help achieve get where you need to be.

Mean time OP had a good weekend. Suckin gas and haulin azz. Best feeling in the world.

So where did your final jetting and PV end up? Are the motors jetted the same or less on one?

Starboard engine is jetted 90P/95S port is 88P/91S, both have 4.5 PV, now show nearly identical air fuels, both rpm equal also. big difference in jetting on carbs but I was also told not all carbs created equal, as long as air fuels look good it don't bother me.

I don't know if this has been covered yet, but when was the last time you cleaned your flame arrestors? Mine appeared clean, but I pulled them and I gained 8 MPH. Every time I would go out in the boat I would go slower. I was down to 72 with the new props, I was like WTH. I stopped pulled the arrestors and back to 80. Put them back on, back to 72. If you haven't done it, clean them. It might be your issue!

found issue, read back a little lol

as far as arrestors, they are not much there, only 2 windings, not dirty.... I took out a lot of windings to not restrict, still wanna run boat once without them to see if I can gain even more speed or rpm...

So it was just a bad coil. At least it was a simple fix once you found it.

Start from beginning and read OP and all post to date. You will find the fix interesting.

I was messing around last weekend and pulled the FA off of my NA 502 and was shocked how it fattened up over a full point on the AFR and was erratic. I didn't play with it much but things went backwards in my case. Just a cheap Holley 3x8" FA.