I run two. A 125 up front and a HDS 5 beside the console.

Could you takea pic of your s/s transducer mounted on your trolling motor? I've been thinking about adding a 4th unit for that purpose but I have heard that there is alot of interference and distortionon in the s/s view when you engage the trolling motor. Im also assuming you have to add an etherenet hub for the forth unit. Is that correct?

My last rig I got away with running one graph and here is how I did it. I bought the biggest Humminbird unit I could get with the latch on base which in the current situation would be any of the 700 series units. The unit came with the transom mount tranduscer and a base. I bought one extra base, a power supply cable, and a trolling motor transducer and mounted that up front. I left the ramp with the graph at the console and when I got to where I was going I unlatched it and snapped it in up front @ the trolling motor....Saved some $$$$......

Two HDS 8 units. One flush mounted in the console, then one up front on a RAM mount. About to get a HDS 12 touch

on last years FX20 I ran an 1198 on a ram mount and a 998 in he dash for the rear and an 1198 on a ram mount up front...On my 2014 FX20 I am going with a Bass Boat Technologies dual mount at the dash with twin 1199 and a Bass Boat Technologies bow mount with a single 1199. I like to be able to run my Navionics chip on one screen or maybe split it with sonar and have down/side scan on the rear, all depending on depth and time of year.

I'll get a pic in a few days, I have the standard Lowrance side image transducer mounted on trolling motor with a protection bracket from transducer saver.
I have never had any interference from the trolling motor.
I have two LSS 2 units, one for two units up front and one for two units on console.
These are tied together with etherenet cable.

transducer

Haven't ran one yet, but about to put one on bow.

3

I run the 9 touch on the bow and 12 at console. works well

I have an HDS8 at console and an HDS7 at bow. Works well for me as I do a split screen with mapping/sonar on each unit. My experience over the last few years is that these units only last a couple of years and Lowrance can't repair them after that as the parts necessary to repair them are obsolete. Lowrance will give you a couple of hundred dollars of credit towards the purchase of a new unit only. Once your units are out of warranty you are on your own. Both of the units I bought last spring are supposed to have two year warranties is the reason I bought them.

Only two for now.

I run 3 with the possible addition of an ipad in the next couple of weeks
A 998C HD SI Combo on the console, a 958C HD DI Combo on TM, and a Lowrance Elite 5 HD in the dash as a dedicated GPS
The ipad will have Navionics on it and Google Maps, I know its overkill but, I hate screens split more than twice
and I like the fact I can run Navionics and Lakemaster chips together and kinda get the best of both worlds
and have a complete satelight view of the lake.

520 in dash,898 ram mounted and HDS 7 on the bow

Only need one. Garmin echo 550 at the bow.

Elite 7 dash , and mark 5x on bow