So it turns out that the high pump outlet hose was not connected to the the hose that runs to the through-hull. The two are not the same size. Thus not only does the high pump not remove any water from the boat, half the water the low pump gets up to the through-hull runs right back down that disconnected hose which should be hooked up to the high pump and back into the bilge so the low pump has to get it back up to the through-hull all over again, where some portion of it runs back down the disconnected hose, etc., etc..
The high pump does get the bilge water circulating at an impressive rate
though, I will give it that.
I'm darn glad to know these things before the water around my ankles lets me know.