Just ordered a HDS 7 and structurescan and would like to know if you use both transducers or just the one that came with the structurescan?

The Structure Scan transducer only has the Structure Scan frequencies. You need both and to overlay the technologies, you need the transducers within a foot of each other.

thanks

It's strange that this information is not in the install guide.

This is a bridge with the overlay activated. If the transducers are too far apart, the two views won't line up with each other.

I have one more question. Along with the Hot & ground wire is a yellow wire that is for a switch on the dash. I only have three switches on my dash that are being used for lights bilage ect... Do I need a switch to turn the structure scan off so I don't drain the battery when the boat is not in use? Or will the structurescan power down when I turn the HDS 7 off?

If you connect the yellow wire on the LSS1 power cord to the yellow wire on the HDS7 power cord it will power up and down with the HDS unit

Wiring the LSS yellow to the yellow on your HDS is certainly an option, but I do prefer to wire the LSS yellow to an independent switch.  If you have no available ACC switches factory-installed, you can just add an additional toggle switch.  Wired this way, I can turn the LSS on and off when I want to.  This conserves both battery power (for example, while tourney fishing and running livewell pumps all day) and longevity of the LSS transducer.  I see no reason to have it running when your are not using it.