Originally Posted by mmwjr
The float switch should be wired directly to the batteries so if the float raises the pump turns on no matter what position the battery switch is in. The helm switch bypasses the float and should only be used if required.
There are two schools of thought on this. The factory wires it through the bus panel because this allows you to isolate the circuit using the "issolation" (Battery) switch for safety purposes. Otherwise, you need to disconnect the leads from the batteries.
It's also not advisable to overload the battery terminal connections with uneccessary direct connections. Wiring to a single battery is a single point of failure should that bettery die. Using the isolation switch you can choose which set of batteries is being run on.
While running, you can ensure that you're bilge pumps are on the battery beign supplied by the alternator.
(I know don't get me started on running batteries on BOTH off of a single alternator).