i got twin 500efi with a 4blade 27p props, in 38zx full of fuel or almost empty can only get 67mph on gps at 4600-4800rpm. if i trim it out a little more i can get 5000rpm but it also drops a mph off. i know the boat is big and heavy but i thought it should run 75

Your speeds do sound like they are down.
Going from memory I think the 500 efi's should be spinning 5000-5200.
Dropping mph while trimming to gain rpm tells me you are over trimming.

Well yeah its over trimming i just said that so people wouldnt say to add more trim.

Yeah, sounds like your over-proped.
The 500efi's spin to 5450.
Not that i know.