Originally Posted by Wet_Boots
Thing is, a 3-wire pump is never directly connected to a pump relay. It connects to a control box, and it's the control box that connects to a pump relay, and so on back to your sprinkler controller.
If it's actually two power wires and a ground, then you have a two-wire pump. Easy enough to check with an ohmmeter.
The one pictured looks like a two wire because there are only 3 wires going "to the pump" the yellow does make it a bit confusing though.