I pulled the water pump off of my 270 and sent it off to be rebuilt. I'm finishing a rebuild on the engine and had the pump rebuilt to be safe. When I got it back it spun like a new pump. When I installed it last night I found that it was hard to turn by hand. The pump turns freer the more I back out the mounting bolts.

This is the original pump off the engine and is installed with new gaskets. It seems to be binding. What gives? What am I missing?