I have begun a process of engine gauge replacement, and while our engines are Cummins (mechanical) , some of what I'm discovering (I think) may apply. Perhaps tangential, at least...
First, our boat started with Faria analog gauges. I now learn their temp gauges (at least, probably others) work with Teleflex senders, which will usually have one wire from sender to display (signal/ohms).
The new temp gauge is from CruzPro and can be calibrated to an IR temp gun, but also gives the easier option to select from 5 choices (three VDO versions, Teleflex/Stewart Warner, and Cyberdyne).
Cummins engines are usually delivered with VDO senders, which usually have two wires (signal/ohms, and ground). Our senders have two wires. (I can't quite see well enough into where they live to find a part number...)
Our Faria gauge have always read low. When I selected the Teleflex option for the CruzPro gauges, they read equally low. Theory we're working on now is that there always has been a mismatch between temp sender (probably VDO) and gauge (wants Teleflex, and isn't user calibrate-able).
Over this coming weekend, I intend to experiment with the CruzPro settings, to see if a simple menu selection will cause more credible readings.
And then of course we'll double-check that with an IR temp gun anyway. There's a potential for a feeling of false precision with digital gauges, so I'm not intending to overdue reliance on the gauges themselves. OTOH, the new gauges also have built-in hi and lo alarms, and also built-in backlighting at various levels... so I can also eventually remove some of the wiring behind our dash that's devoted to gauge lights.
If it matters, I've also already switched to Aetna digital tachs. They only wanted to know how many gear teeth, simple menu setting, instant accuracy. The Faria calibration process was a lot of trial-and-error, with accuracy at one RPM level, increasing error the further away from that set point.
South River, Chesapeake Bay