Any suggestions on Sonar problems?

[Jaw Breaker]

I have a Lowrance 102c fish finder and a Garmin 172c Gps on the console of my boat. I have a Lowrance X71 on my bowmount. The two on the console were brand new last year and had no problems. This year there is problems, when I go to start my motor the two on the console blink while the engine is turning over. Then every once in awhile my fishfinder goes crazy and gives inaccurate depths, when moving and stationary. And I also am getting interference when the finder on my bow is on with the one on the console. Similiar when you run two Vexilars to close together ice fishing. There are verical color fragments on my screen, the I shut the one off front and it goes away. Bad wiring, bad connection, bad transducer?

[wally-eye]

Usually the interference is caused by one graph having more power than the other one..............depends a lot also on how close together the transducers are to each other. Think one is just overpowering the other.

I run two graphs but mine are not that powerfull so I don't get the interference but I know other people that have 2 graphs and they usually can't run both together without having the interference.

Usually when I'm in the front of the boat I just turn the one on the dash off. Not sure about when starting the motor.