running out of breath in the 1/4 mile

????Read the link that you added to the actual Carter spec.....25 GPH.

Then look at the pump that the OP pictured in this thread....We had another fellow on here with the same type of pump and the same issue within the last year.

I can't say that no pump in that case could ever flowed 40-50 GPH in to 4-6 psi, but the Carter M6866 spec is crystal clear. And I ain't pickin' on anyone, but why go by an eBay listing when the manufacturer's specs says otherwise? Maybe I am missing sumpthin' here.....