You leave the tranducer on the menu to Hi def side scan, the y cable 2 transducer set up will switch automatically, you dont have to select a different transducer. I have 2-997s on my boat, the console unit has a transducer in the jackplate which is out of the water on plane , and an in -hull transducer that gives you depth readings at speed. You will not get side scan at high speed. This was from another site in answer to the same question. I dont know for sure hes right, but he seems to know what hes talking about.
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