Transducer interference?

The boat I bought has 2 Helix 9s, one on the steering console (si) & one up front (di). When running both units i get long verticle lines on the sonar but if i cut one unit off the other clears. It dosent seem to be the trolling motor causing it. Any ideas how to solve this problem?

you've got 2 depth finders running on the same frequency either change the frequency or turn one off is about all you can do

I have a long way to go understanding these electronics. I'll try to figure out how to change frequency. In mean time I'm going to take it back to the dealer & let them check it out. I shouldn't come with 2 units if it is not capable of running 2.

Replace one of them with a Helix 10 SI MEGA. You'll have more to learn, like me, but the difference with the 10" screen is amazing.

The difference between the resolution in a 9 and 10 is definitely worth the extra money. I've got both.

there is no need to run both use the console when searching use the bow when fishing you should be able to hold the off button until a menu pops up you can turn the sonar off at either one without shutting the unit down you just tap the power button again and it comes right back on no start up time. I have to do this it's not as aggravating as it sounds once I find my spot I hold the button down, suspend the sonar then hop up front drop the trolling motor and fish when I get ready to drive again I suspend the bow real quick sit down behind the wheel and tap the power button it pops right back up. you get used to it it's just a couple buttons to press.

I run 2 older SI units and they both work at the same time.

I've got 2 MEGA's that run at the same time with no interference.

I have a Helix 7 SI at the bow and a Helix MEGA 10 SI at my console and run both at the same time sometimes. I may have the 7 on DI and the 10 on SI and turn the 10 screen toward the bow, on the gimbal mount, so I can have a bigger screen to view SI with. Never had any interference between the two though.

I've got a 10SI at the console and a 9DI upfront, never had a bit of trouble with that 10 at the wheel, but that 9 upfront has been a total cluster the whole time. It's flush mounted in the bow (2016 Ranger), and about 50% of the time works fine, but the other 50% it'll read 874 feet deep, 369 degree water temp, and occasionally will just get screen interference. Seems to do it mostly in shallower water, but will do it no matter the depth or bottom composition. I've grounded my trolling motor, you name it. I also installed a heading sensor puck, which I intended to flush mount at the bow too, but had to put it next to the console because of electronic interference. You can run a magnetic compass all over the front 3' of my bow and there's interference coming from somewhere.

Well, my niece's fiancé is the main "rigger" at Wedowee Marine (maybe the biggest Phoenix dealer in the state), that rascal is a wizard with these electronics. So back at Christmas I was lamenting to him about all this and without knowing, he asked, "You got Humminbirds, right?" I said yes, and he said, "live with it, you ain't gonna fix it." Apparently this is a widespread issue.
He did say I could probably get the new Ultrex with the built-in transducer and eliminate all/most of it, but most likely nothing else would work.

I dropped it off with them this morning, hopefully he will be able to figure something out. If not they can swap them for something that will work.

Turn the depth setting off auto and set it to 100 ft or something.

Hadn't considered that...I'll give it a shot!