Hello, I've got two 2001 Mercury EFI 250 Saltwater engines with OEM Mercury gauges but without temp gauges which I would like to add.

The engines have temp sensors in the starboard heads and are connected to the harness which I assume goes to the light/buzzer in the helm.

What is the best way to incorporate temp gauges as well? I'd rather not lose the idiot light and buzzer.

Do I need to mount an additional sensor in the port heads and run wiring to helm or can it somehow be patched into the exiting harness?