5.7 mercury water pump impeller replacement issue

[MadapeedJames]

2001 chaparral 230 Ssi with the 5.7 merc. Had a bad impeller on my water pump. Ordered a new housing and impeller. Replaced with very little issues. However once I start to tighten the housing to the pully the impeller gets stuck and won’t turn.
I first found this out after I replaced the pump and started the motor. The serpentine belt would not turn the water pump pully.
after taking it apart and putting it back together making sure the impeller fins were all in the correct position several times I found that I could spin the pully by hand all the way up until I started to snug up the 5bolts around the housing.
I compared the old and new impellers and housing same part numbers and seem to match up size wise. I am at the point of ordering a whole new pump with the pully assembly already attached. (Several hundred $$$ vs the 50$ impeller and housing)
Or maybe I should order a new impeller?
Note when impeller is pushed down as far as it can go it presses against the wear plate. I believe when I tighten the bolts it’s locking the impeller down.
many thoughts or suggestions are greatly appreciated. Thanks for taking the time
North Carolina

 

[spannerman]

Have you checked that the impellors are the same length? I always assemble water pumps with some waterproof grease which helps seal and prime the pump quickly and gives the impellor a smooth start to life.