My suggestion to you is buy a Lowrance.

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I have temp readings on my trolling motor locator (Garman 250C) and on my main locator (Humminbird 565). They have different temps by about 4 degrees. Today I checked with a couple other boats on what theirs read and they were running 47 to 48 degrees. Mine was 41 on the Garman and 44 on the humminbird. Does anyone know if these can be recalibrated?
My suggestion to you is buy a Lowrance.
Usually the trolling motor sits down in the water a little further and could be reading a little cooler water.
Last year I bought a AquaVu DT-100. One interesting thing I learned was that the water temps (during summer) stay within 1 degree all the way to the thermocline, sometimes down to 20'. One Garmin (trolling motor) reads the same temp as the DT-100 while the other Garmin (transom mount) reads 2 degrees different. I figure temp scales are man made and can be any figure so if the scale goes up it is getting warmer and etc.
I also have the same garmin on my trolling motor, and a Lowrance 522 on the console. The Garmin is always 3-4 degrees colder than the Lowrance. So it must be something with the Garmin, because i would think my Lowrance is correct.
I tried to cover all bases so there is a Lowrance on it too. It does read much closer to actual. After reading the advanced mode I found I could adjust the hummer so it is now right on.
Msgmills, I would have thought the same thing but the sending units are all mounted on the transom within three inches of each other. Guess I will just have to add 5.5 degrees to the Garmin.
