Good morning, just bought a new to me - Ranger 1850RS, it has a HDS7 Gen2 non-touch in dash and a HDS5 Gen2 non-touch in the bow. I'm relatively new to sonar, but my question today is about transducer options. On the 7 it appears to have a through hull down and the 5 in the bow is connected to the Terova trolling motor with built-in transducer. If I want to add side scan and what is my options for - LSS2? Additional advice is welcome. Good fishing and good blessings.

Your HDS7 in hull transducer is for 2D Sonar. You will need a LSS 2 transducer mounted to your transom or jack plate to get down and side imaging on the HDS 7 console unit.
https://www.lowrance.com/lowrance/type/sonar-transducers/structurescan-hd-skimmer-transducer/

You can purchase a 15' Ethernet cable to connect between the HDS 7 and the HDS 5 that will allow you to view the down/side imaging from the LSS 2 transducer on your bow mounted HDS 5. https://www.lowrance.com/search/?q=ethernet+cables

Bauman, where are you located. I recently upgraded from a HDS Gen3 with LSS2 transducer to HDS Carbon with 3 in 1 transducer and still have the LSS2 transducer that I can give you for the price of lunch.

Thank you so much

@hookatoad just north of Dallas in Prosper

Your units will require a Box for Downscan and Side Image. You cannot get the structure Scan with out a Structure Scan HD Box.