Temp Gauge indicates Hot, But engine is Not Hot

[ShoreFlyer]

I have a 7.4L EFI Horizon Mercruiser Raw Water Cooled. The temperature gauge has been warming up to about 200-220 deg.

1. The computer indicates is running at 158-163 deg. (mercruiser scan tool)
2. I have changed the sending unite twice.
3. I changed the Thermostat.
4. Changed the Thermostat gasket twice, it does have the brass rivets in it.
5. Changed the gauge twice.
6. Hooked the gauge up directly to the battery using new wires. New wires to sending unit. by passing he harness.
7. Engine is normal to the touch.
8. Used an Infrared gun to take temps. Seems normal
9. Manifolds and Risers changed last year
10. New Water pump last month. It had broke.
11. The Alarm doesn't go off.

The engine doesn't appear to be overheating, as confirmed by the mercruiser scan tool. I believe its an issue with the wrong resistance going to the sending unit from the block. But I can't pinpoint what would be causing this.

Andy ideas ?

 

[Thornton69]

Is it possible you are replacing the wrong temp sender?
Have you tried wiggle testing your harness to see if it changes the reading on your gauge?

 

[ShoreFlyer]

its the correct sender, One for the gauge, One for the computer. I unplugged the harness to clean the connections, but they were clean as a whistle.

 

[Msauder123]

Check sender connection, and wiring connections not just at sender (use schematic). If all checks out try sender.