Could there be a common link to make one set of gauge all read lower than the other?

I noticed for the most part all of the gauges for the port side are low... or the starboard is high I guess either way.. lol
volts, oil pressure, oil temp, etc..
For example my port oil temp never shows more than 140* the others side is around 155* or so.
voltage is around 11- 12 the other side 14v.
The Tach is low 300rpm till it gets to 3-4K and the it catches up..
possible ground issue?
Both motors rebuilt 50 hrs. ago (Tyler Crokett 500efi)

I would take one of the sender wires off of the oil pressure or temp gauge on one motor and attach it to the sender on the other motor and see if it changes. You could do this by just hooking up a jumper wire. If it follows, you have a gound issue with your wiring harness at the helm.

FWIW, power to the gauges originates at the ignition switch, goes thru the lanyard, and eventually ends up back at the coil. You might get a DVM and measure voltage for both sets of gauges. I noticed that mine jump around when I turn on my nav lights. My laundry list includes running a separate power feed up to the help to supply power to all of the lights, blowers, etc.

Sounds like a poor ground as mentioned

Check all of your grounds. Also check the multi pin plug that goes to the engine for green stuff. Make sure it is clean and then put some di-electric grease on all of the pins before reinstalling.

You can also swap wires at the kill switch and see if the problem jumps sides. I had a similar issue once, so I rewired the kill circuit with 2 relays to take the strain/load off of the kill switch. Have you looked at how thin the wires to the switch are ??? Very thin !!!!!

Great info, gives me a place to start..thanx!