Temperature gauge responds to outdrive trim and acts like my trim gauge...

[Xxvisionrider]

Ok, I have a 99 Chris Craft 210 Bowrider, 5.7GS. I have replaced my trim and temperature gauges. I also used alternate power and ground on both gauges to test isolating the two gauges from a common grounds and power during testing. Even while isolated I had the same results. I just read the complete test procedure and the temp sending unit testing procedure. I will try that tomorrow as well as take my multimeter to test for short circuit. I want to just run a new wire but would prefer to locate the short if possible. If there are any particular locations in the wiring harness that is a known problem area I would love to know.
When the outdrive is trimmed up the temperature gauge rises with the actual amount of trim.
The trim gauge just stays pegged full up trim.
The motor was pulled and rebuilt last year before I bought it.
At times underway they will both revert to proper gauge indications.
I have a short....somewhere or a loose connection in my best guess opinion. The trim sending unit has not been replaced and I'm selling the boat and don't want to put $150 more into it.
I will check for thread tape at thermostat housing and test the temp sender.
I just want to make sure I'm on the right track in suspecting two wires (temp and trim sending wires) are copper to copper somewhere along the line.

Thanks in advance for any info.

 

[dypcdiver]

I'd suspect an earth/ground problem, common to both gauges.