Well damn! Installed the new impellor... fits snug, all the way to the face plate with no gaps, new gasket, etc. Ensured all the hose connections were tight from the hull intake to the exhaust risers. Took it out on the lake and the boat ran HOTTER @ 180 - 190 F. Although it stayed consistent and didnt fluctuate more than 10 degrees between underway and idle...
So out of shere desperation, I took out the thermostat and it ran at a VERY cool < 100 (underway) and 110 (idle). It still runs O.K. but the motor wants to hesitate out of the hole cause she's not warmed up... I'm gonna go to NAPA and try out another 160 F thermostat - hoping my other NEW one is not opening fully at 160 F (thier cheap).
If that doesnt work, I'm officially out of ideas short of pulling the recirculating pump. The recirc pump appears to be fine, its not loose, not making any noise & turns smoothly with the belt off, etc... Is there a chance the recirc pump's blades are worn to the extent that thier not moving the hot water well

Its not like the boat is overheating @ 180 F, but its driving me nuts cause it SHOULDNT be that high...
Thanks guys! Joel