I'm looking at a HumminBird 409850-1 Helix 7SI GPS/FishFinder with SideScan , i know nothing about this unit , Any information or advice would be helpful i've wanted a SideScan for a long time & their finally going down in price a little bit . I don't want a screw up & order something i will regreat. I've always bought Lowrance GPS/Combo & i had Sonar & gps , does this.

Humminbird has Side Imaging--that what the SI in the model name means. Lowrance has Side Scan.

 

Look at the posted images on the Electronics forum.

 

The model you posted has been discontinued. It has been replaced by two other 7" display Side Imaging models.

Helix 7 CHIRP SI GPS G2

Helix 7 CHIRP SI GPS G2N

 

Both have CHIRP Sonar and CHIRP Imaging and GPS/mapping. Both have built-in Auto Chart Live to create HD contour mapping in real time to the unit's memory or to a ZeroLine card ( has several million shorelines to contain the created contour lines).

The G2 is a standalone model.

The G2N is networkable to other Ethernet capable units.

All three have 83/200 kHz 2D sonar and 455 kHz Side Imaging and a Down Imaging view created by blending the two SI pulses.

 

All my current sonar/GPS models are Humminbird Side Imaging.

How does it compare to the Garmin EchoMap Chirp 73 SV ?

Be sure what model your going to buy. The older unit can't be connected to others. But he new 7's can be hooked up to the bigger models. I have a Helix 10 SI and love it, and was going to buy a second 10DI for the front. But may go with the new 7 as it will allow me to link it to the 10 and my trolling motor. Only issue is the 7 and even 9's are nothing like the HD 10 and 12 units. I had one of the first SI units 987c SI for years. This 10 is so far advanced from that its unreal. 

Can't help you out on how it compares to others. As I have only ran Humminbirds the last 30+ years.

Pete