1993 200hp won't rev past 4200

[Glinley]

I have 2 93 200hps on my boat. The port side revs right out to 5300 but the starbord only gets 4300. I've rebuilt and swapped carburators and fuel pumps. Replaced the filter on the engine and cleaned the seporators on the boat. Compression tested all cylinders and there 120 to 115 psi. Changed plugs and coils, all cylinders are firing. Removed the intake and checked the reeds. Still can't get it to rev out. Possibly an issue with the electronic ignition?