Preston,
I agree with Dorado and the others. I have had smaller units, but have come to a personal opinion that a 7" unit is the smallest I want to run. I have a 7" on both bow and console, but am saving for a Helix 10 at the console. Kinda depends on how you use them. I like running the GPS and sonar at the same time on a split screen and in shallows run side imaging too, so the larger display accommodates the multiple views with enough size and resolution to be useful. Also, when trolling or drifting and spooning the rear admiral (my wife
) can see the display from the stern, where she likes to fish, well enough to see fish, depth and temp....but better yet, and really important in my opinion, can see her spoon falling and stop it and control her spoon depth when spooning for Stripers. She is about 8'+ from the display but can see it from the stern well enough to reference.
I am usually on the bow when electric motor trolling and can see the 7" (Helix 7 of Lowrance Chirp 7) pretty well whether standing or sitting on the butt seat up front. So the 7 works pretty well for me up front. I had a couple of smaller displays up front on the bass boat and it was tougher to see what I wanted to see. I generally only run the Sonar on the bow, no mapping usually, so the 7" is good because it is full screen display Sonar.
As you know, our Terrova's with the US2 transducer, will only Sonar, so no down or side imaging with out adding a transducer to the motor on the Terrova. I think one of the benefits of the US2 transducer is that it is protected by being installed in the motor housing. I like that. I have torn up the transducers mounted on an ancillary bracket to the motor housing. But that was generally shallow lake fishing.
Last comment, Dorado is right. The major reason to run the fishfinder from a house or starting battery (and not the trolling motor battery) is to separate the power sources. The Trolling motor, when running, typically creates a bit of " RF noise" that can be propagated on the DC cable, often resulting in various issues with the fishfinder electronics, i.e. power shutdown, loss of depth reading, display distortion, erratic readings, etc. The transducer is only powered by the display head unit. The US2 does not receive power from the trolling motor, only the cable from the head unit, so as long as the power to the fishfinder is not from the trolling motor battery(s) you are generally isolated, at least from a hard wire connection. However, the interference can still be an issue due to just being in proximity to the source, usually the electric motor, or even your big motor or kicker, so rerouting the wires to get separation or adding the little snap on ferrite bead "chokes" can be helpful.
I don't get any interference to the fishfinders from my Terrova when running at any speed, but the trolling motor runs from its own battery bank and the fishfinders run from my house battery, which is isolated from the starting battery by an automatic relay for charge control. There still was no interference when the starting battery and house battery are configured parallel either, just for the record.
Sorry, I get into the weeds pretty easily, lol
Hope that is helpful. We plan to put it into practice over labor day weekend, wish us luck!
