I will assume you are talking about a temperature gauge.
You will need to buy a new 54 gauge and capillary sensor. Sold as one unit. Click
Adapt it's sensor fitting to the 57 motor as necessary.
I assume when it broke/was cut off, someone plugged the sensor hole with a pipe plug.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn