white sludge coming out of water intake.

[wellcraft 5.0 volvo-penta]

Overheated the engine due to a shreaded impeller in the cooling system. When I got it out of the water I noticed a white sludge solution as well as a few plastic impeller pieces running out of the water intake. Anybody have any ideas about the white sludge solution. I already replaced the impeller and cleaned out the coolant lines, but after running it again in the driveway and disconnecting the water, more white sludge was coming out. Anybody have any ideas or seen this before