Did the PO of your boat leave the country or something?
Let's just say the PO apparently sailed the boat, but never bothered to learn anything about the boat's systems. I did ask, but the PO said they never tried using the manual bilge pump even once in 6 years of ownership...
Anyway, I talked it over with the marina owner and he also felt that it's most likely attached to a bilge strainer that's screwed down somewhere under the shower pan. (It wouldn't make any sense for the manual pump to be connected directly to the shower drain). And the only available access to that area would be by removing the toilet and trying to get at it through the fiberglass base. But he believed as I do, that it was a bad position for the manual bilge pickup.
Not feeling the urge to disassemble a perfectly working toilet right now, I just stretched the pickup hose out as far as I could, cut it off, and the remainder retracted back into the pipe that feeds under the mast. I figure if any water comes out of it, it'll drain back into the bilge anyway.
So my electric is now in the lowest part of the bilge just behind the mast, my manual bilge strainer is now about 2' aft of the electric, and they're both working nicely.
I figure the manual pump will be more for emergencies anyway. So being at a point just slightly higher (1/2") than the electric seems like a perfectly acceptable location to me.