If I want to power my bilge float switch then I'll have my battery switch to #1 or #2 and have everything else on the boat off. It's basically the same thing where the only draw to the battery could possibly be from the float.
If it's an Explorer he should have a box like this in the aft end....How it is wired depends on if it had a factory option battery switch or whatever strange things a PO may have done!