Maybe the water pump hoses were reversed upon reinstallation, during the impeller change. Check that and the impeller-they frag very quickly without water. Was the transom bellows and hose serviced? Its easy to twist the water inlet hose and restrict flow.

It's going back to the dealership this morning.

I'm hoping there's no internal damage to the motor....

http://m.youtube.com/watch?v=uLX6kvWKNJc

stock 496 have 160 thermostat so they they run about 180-190 and if they over heat computer shuts it down I say you will be fine ,open the right side of the heat exchanger and see if its has any blockage . I do not think its a cooling issues .check your iac motor. please let us know what you find

be very careful, in my opinion 496 is a grenade, turn the key=pulling the pin..see to many fail with low hours for B/S reasons...working on one now volvo POS 30 hours, internal fuel filter clogged(have to replace fuel pump..big $$$$ and now killed a piston...volvo no help even with 30 hours....

so I picked the boat up from the stealership today. apparently it needed a new sea water pump after all. i KNOW they told me that they were putting in a new one before I took delivery but today they told me that they said they only replaced the impeller. If I hadn't thought I got a new one to begin with, that would have been my first thought but it is what it is. Thanks for the suggestions guys.