1990 evinrude 70 hp temp sensor alarm & SLOW mode

[Nick475]

I have a 1990 Evinrude 70 hp that the temp sensor alarm activates and the motor goes into SLOW mode. (Continous alarm sound)
I've replaced the temp sensor and put in a new impeller and water pump kit.
The motor continues to go to SLOW mode but the head temperature is not hot and the pump puts out a strong stream of water. (even stronger with the new kit installed)
If I disconnect the tan wire from the temp sensor the boat runs ok.
If I reconnect it again the SLOW alarm goes off.
Model is VE70TLES B

Thanks in advance for any ideas on how to solve.
Nick