A short clip. Trying to keep my old boat sailing. This time, removing and testing thermostat and temperature sensor. Volvo MD2b

Hello, My yanmar 2gm20 has what appears to be a custom sensor wired to a custom gauge instead of the switch type sensor and the alarm. I don't find any mention of that type of things in my service manual. I would like to replace the sensor but would rather keep the gauge if possible. Is there...