Interference typically happens when two units are using similar frequency bands. There are some times when resonance frequencies or sympathy frequencies are an issue but that is rare.
Try it out and if your screen has too much noise when one or the other is on then try adjusting the frequency of one or the other. Personally I would keep a log of adjustments so you avoid confusion. Remember that you can always “reset” both units and start again.
Do you have a picture of the trolling motor shaft with everything connected?
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