I have some temperature irregularities. That's always been true for me as I run several units. Never had 2 give the same temp even if the same brand. Here is one record.
Lowrance 66.9
Vexilar 66.5
Garmin 63.98
Fish Hawk 66.1

It really doesn't matter that much right now, but earlier in the spring it can be of help to know the precise temperature. Any ideas?