These types of kill switches are normally closed when the lanyard clip is pulled out of them, as in ‘Man Overboard’. With the clip installed, the circuit is open, allowing the motor to run. The motor can be shut off in two ways, either by pulling the clip out or pushing on the button. Keeping the lanyard in your pocket while the boat is unattended will also act as a theft deterrent.
To install one in the original position, why not screw or rivet a piece of thin aluminum plate over the original hole and drill a hole in the plate to fit this type of kill switch? Can you post a photo of the one you have with six terminals? It seems more like an ignition switch.