I run an 859ci DI GPS with an older Lowrance LMS339 on my 19ft boat. I get no interference on the screen, but my Lowrance ducer is on the left side of the transom and the 859 ducer is on the right side. Humminbird told me that any 2 transducers can cause interference with each other if they are mounted too close to each other, regardless of make or model.