i will check the linkage on friday. hopping it is somethnig simple. i was almost ready to have my prop sent out to be labbed but know im really confussed with the top end speed and rpm.

I hope they set the preload on the upper bearing set properly. I have seen a few stock from Merc that were wayyyy over torqued. Youll know soon if they overheat.

Dont change anything till you identify the problem. If you change the prop, you'll never know what is what.. One step at a time. Qualify the motor like everyone suggested. Make a run and pull the plugs, see if you find anything different from cylinder to cylinder. Do a compression check. If all seems well with the motor. Pull the drive and see if there is any binding.. If it were that tight it would have burned up a bearing and locked up I would think.. But stranger things have happened.
Did you quiz the mech that did the drive about gear ratio? If he changed it.. and wont tell you a smaller prop should bring you back to speed... Just some ideas, but the last thing changed was the drive, so it may be the culprit...

Let us know what you find. Good luck..