1999 150 xr6 will not run over 4500 rpms Help!!

Alright let's start from the beginning, I bought this boat (18ft kenner with a 1999 150 xr6 2.5) from a family member I knew it was not running right but I thought I could easily fix it. So the motor normally runs 5500 + rpms right now its only running 4500 4600 rpms, we've cleaned carbs tank replaced fuel lines ect, just to cross out it being a fuel issue, still no difference, runs great just won't go over 4500. Compresion is 150 on all 6 BTW. So we brought it to a mercury tech to get the electrics tested his response was everything looked good except that when he would rev the engine the stator did not pick up the voltage as I should have so he recommended I change the stator so we did. Took the boat out and it ran like a bat out of hell for two minutes reaching 5500 rpms with ease I was completely shocked but that only lasted 2 minutes then back to running at 4500 so we put it on the trailer and immediately checked spark, found that i had no spark on the starboard side only hitting on 3 cylinders. So we decided to replace power packs and I gave us our spark back which was dark blue and I could pull my plugs over a half inch while sparking thought we fixed it took it back out and it didn't even try to get over 4500. Everything still had spark, thats us checking with boat on the trailer. I'm really getting aggervated at this point please any help, advice would be great