Mag 7 pump

I have a Mag 7 pump as circulation pump underneath my 125 gal. I am about ready to throw the thing out the window. I dont get hardly any water movement from this pump. The box says high pressure, could that have anything to do with it? The pump makes a clacking sound as it runs. I have taken it apart several times to see if the impeller is jambed or something. I dont know what to about it, any suggestions? Thanks

 

See: Replace Mag 7 Impeller

 

First off its to small for any thing in a 125 I ran 3 9.5 mags in mine the clacking sound is the impeller engaging the shear pin of the shaft .. Are you trying to cycle it one and off like a wave maker ? can't do it to much torque will ruin the pump and over heat the shaft housing. You want high volume for this appaclation not high pressure But it should move water around with no head pressure on it.