My boat came with a rule 500 2-wire auto pump. I have an on/off switch at the console. My replacement has 3 wires. How do I connect the 3 wires and still use my on/off switch?
Good after I used to be within the navy, electrical energy was once three phase. There was once no original. Considering the fact that its is a pump, my recommendation is disconnecting the pump out of your load. Go ahead and wire up your pump inserting the 3 wires on any terminal. If the pump rotates in reverse, stop the power and swtch any 2 wires and you are good to move.
It all depends on the function of the third wire. The instructions that came with the pump should tell you what it's for. If you're only using the pump with the switch you only need to apply 12V and a return to the pump. The switch could be in either leg, but will normally be in the +12V leg. The third wire could be an earth ground for safety or you might have a built in float switch so that you can apply 12V directly to that 3rd wire. When the internal float switch goes high enough it will turn on the bilge pump for you. Your best bet is still to read the instructions before you install it though...
