Temp sensors in t-ducers are a chip that is fed 5 VDC.
Water leakage into a poorly potted chip exposes 5 VDC to salt water
I'm retd from the business 15yrs now,but back in the day I replaced many bronze
t-ducers with built in temp sensor due to this leakage & the resultant rapid electrolysis
caused by it.
If the boat
couldn't be hauled right away,I cut the +5 V wire at the t-ducer plug
Moral of story-if temp readings go crazy-fix it fast!