I have a HB up front on the trolling motor and Lowrance in back on transom, both side imaging. I never have problems with one exception, when I swing that front one around looking for stumps and such, when the side image beams cross the Lowrance transducer in back it will slightly disrupt the Lowrance returns. This is also more pronounced on the sonar than the down/side images. I hardly use reg sonar anymore, so... . I was under the impression that I was able to run both without much problem because they WERE different frequencies. I have noticed what Mark said about other boats, some peoples units will mess up my returns others dont. So I think it prolly has to do more with frequency than anything else.