How long does it take to change a water pump in an 88 chevy celebrity?

2.5L throttle body with AC. I think that I got ripped off some time ago. The garage that did it said it took him 9 hours and he charged over 300 bucks for the labor. So the proper question is what does the Labor book say on how long it should take to replace the water pump. Thank you.How long does it take to change a water pump in an 88 chevy celebrity?i dont know what the labor book says but it shouldnt take 9 hours more like 3 hours