I have 43V Nortech 2011 with 700sc and they won't go over 4000rpm. NO alarms or fault codes? I have changed all the fuel filters, the water pressure, oil pressure, boost pressure, temps are all ok under load going 60-70 mph. I have even cleaned the air filters.I put the engines on Merc tech computer and everything checks normal. ANY ideas out there to help find the problem. Coils or plugs maybe?????? Fresh gas in tank also. 91 octane no ethonol. Call if you want 419-654-1222 Lynn

I thought someone mentioned coils on another thread? Did you pull the plugs?

Check your battery Cranking amps and see if its charging Right at that RPM.

Won't go over 4000 rpm loaded only or even in neutral and bringing the RPM's up then?

Lynn,
It would be odd for both engines to be doing it but check your fuel pressure at 4000 RPMS, scan tool will show it.