Welcome aboard Nancy!!
You should have two circuits. One circuit for the manual switch at the helm and the other circuit for the float switch. Many pumps have two circuits. This allow you to wire the manual circuit from your dash to the pump and the hot circuit to a float switch, then from the float switch to the other circuit on the pump. If both pumps are wired, they may have wired one with the manual circuit and the float switch circuit directly to the 2nd pump which more than likely has an internal float switch. My guess is their logic was the float switch is for when they are away, and the manual switch allows them to double the bilge pump output in case of emergency.
I'd start with the helm and locate the bilge switch. Turn it on and see which bilge pump turns on (if any). At least you know whether the manual bilge pump circuit is working and which one it goes too.