engine breaks up over 5500 rpm

[jps601]

Last year rebuilt carbs at beginning of season. End of season stator chewed up magnetic cup and engine blew. Replace stator, magnetic cup and sensor eye also a bore with new pistons and rings. Engine runs and sounds fine till you get past 5500 rpm and it almost sounds like the rev limiter is kicking in the way it breaks up. engine bounces around super fast between 5000 and 7000 rpm if u hold it wide open almost like the rev limiter sounds when you try to rev to high when its in neutral. I dont think it sounds fuel related but i could be wrong. any ideas on where to start.
1997 Challenger1800 twin 787s

 

[timmyboy76]

open the electric box, (big grey thing), and unplug the red wires from the yellow square thing, then give shot. If fixed, replace the "rectifiers"

 

[jps601]

one of the 15 amp fuses on the mpem blows instantly when replaced. The wires look to run to the rectifier. So Im guessing I have a bad rectifier. anyone ever heard of the fuse blowing instantly even if boat is not running and lanyard is disconnected?