Dale,

The impeller is very securely fastened to the shaft, but that is a thought about the impeller clearance.  The thought had crossed my mind but it is a very difficult thing to measure (kind of like trying to watch the light go out after the frige door is shut :-)   I figured since it was sold that way it must be approiate, but it is an aftermarket pump and housing so who knows.   Before I put it all together I will make some measurements and see if I can figure out the clearance...  maybe with a piece of clay on the impeller blades.

Does anyone have a guess as to the proper impeller clearance?

Dave Leonard