I just rebuilt my OMC 460 engine along with my 850 cfm holley carb. I am only maxing out at about 4000rpm. I should be hitting around 4800 rpms. Any idea where to start the problem solving? Is there a way to test to see if the secondaries in my carb are fully opening? does that sound like a possible cause?

Timing advancing correctly??????

We need more info, what rpm were you running before??? Are you using the same prop???? Make sure your throttle cable is adjusted correctly and opening up completely.....

I am using the same prop as before. Before the rebuild I hit around 4900 rpms

Are the throttle cables adjusted properly-otherwords are you really getting to WOT ? Went thru tha when I redid throtle levers and repowered--

push the throttle all the way open then remove the spark arrest/filter and look in the carb,,are all the butterflies vertical? 'Cause that's open. Then check that timing is doing what it should at speed.