Aftermarket water temp gauge reads low due to wire length

I would suggest that induced voltages would be more likely to cause the display to be erratic, rather than just off by 10 degrees.

I am curious what type and brand of electronic gauge you are using. I just put an electronic gauge on mine and it reads about 10 degrees high. Really don't know if it is the fault of the gauge or the location on the engine compared to the one on my ECM, or maybe both.