Guys,
No one appreciates your knowledge of these boats more than me. But in this case we need to work on some basics. This 'old' pump was fully rebuilt with everything but a new shaft and pump body. The shaft did not have any fins or wear to impede the installation of the new impeller. I did clean up some discoloration near the shaft seal. There was nothing unusual about the shaft itself. New bearings fit tightly and the new shaft seal went on without difficulty. The backing plate was new too along with a new gasket. The impeller installed without any great effort, I did not beat it onto the shaft, it is soft brass and it seemed to fit pretty well and was not overly proud of the pump body when I put the cover back on. The cover installed without any weirdness like if the impeller were not fully installed on the shaft.

I have never rebuilt a pump like this before, but I have more than a bit of mechanical experience. If something was odd about the way I rebuilt this pump it was not some obvious thing. What none of us here have are the specs for the dimensions of the body, the little squeeze piece or the shaft itself. It is these combinations of tolerances that make these pumps work. For sure if the combination or any one particular spec is too far out the pump is not going to work or work very well.

I think the key detail here is that here on the river the water has a fair bit of abrasive silt in it. This is evidenced by the 7 mile long sand bar at the mouth of the Columbia River.
It would be almost worth the time to carefully tear apart the new pump and detail the critical dimensions and record them for posterity. Another possibility is that I burned the new impeller up by cranking the motor for nearly a minute before it started and then since it wouldn't prime it ran for another couple of minutes before I shut it down. At which point I started checking every connection for a leak and found none.

Other important details are that while the pump when primed from above did push water through the motor, the flow rate with the new pump is nearly double that with water at or below the pump level. Nobody wanted the old pump to work more than me, but the new pump does exactly what it is supposed to do and I suspect it will do so very reliably.

When I have time I will tear the old pump apart again because I want the bearings and the shaft as well as the cover, these will be good spares. If I burned the damned impeller up I will take some pictures of it and share them. I have no problem with others learning from my mistakes, it is why I make so many of them cry

Dave Graf