Fish finder problem

[rondog]

I recently installed a 788 as a second unit.I mounted the transducer exactly as the information sheet from Humminbird showed.When both units are turned on the 998 sonar screen shows up like the sensitivity was set too high,the bottom jumps all over the screen and the depth numbers constantly change.When the 788 is shut down the 998 works perfectly.I changed the transducer location from the starboard to the port side of the boat about 4' away,almost no change in the problems.Both units are connected to the cranking battery,the 788 directly and the 998 to a terminal strip under the dash.

[JDK]

Transducer interference when both units are on?  Are both units in the same frequency range.  If so they may be trying to "talk" to each other.

[bigredfishing]

I agree with JDK.   Have you tried setting up each unit using a different frequency?   I would set the console unit at a high frequency (200 khz) for high speed pickup and the front unit on low frequency (83khz) to show more bottom detail.

[Lundin-loading]

Do you gave a bow mount trolling motor? If so I'd mount the ducer on it. A little bend in the metal bracket and a hose clamp and your in business.

[rondog]

I adjusted the sensitivity as directed in the manual,isolated the power source,and ran the units on different frequency's.The screen on the 998 did clear a little when I adjusted the sensitivity but all of the other problems reminded. If I mounted the transducer on the trolling motor head there is about 5' of slack cable when the motor is in the stowed position which would create a different problem.
I'm done with it ,I'm taking it off today and replacing it with the HD model  and selling the CI
Thankx for the help