1158c DI noise issue when trolling

I have the 1158c DI on a 20′ North River, when I run on my 140 hp main motor the sonar, 2D and DI are clear as a bell, up to the point of course of when I speed up.

I also have a 9.9 kicker motor, and when I troll at slow speeds (under 5 mph) I am getting noise on the 2D sonar and lines on the DI. I have done some troubleshooting and what I have found is the tranducer does have some play in it. The play is related to the transducer mount and not necessarily the transducer it’s self.

Has anyone else had a similar problem? The transducer mount I have is the one that allows the transducer to kick up if you hit something.

Any help or guidance would be appreciated.

Do you have resistor plugs in the 9.9? Sounds like interference more than transducer wobble. Test it while no motor is running and wiggle the transducer.

The boat and motors are all NEW, I am not sure if there are resistor plugs in the 9.9 or not, will I be able to tell by looking at it or will I need to remove it to get the number.

Without the 9.9 running or when running on the 140 the picture is very clear and clean.

Have you tried wiggling the transducer with the motors off. You can do it on the trailer. You did not mention the make of the 9.9, but all the resistor plugs should have an R in the number(BR6HS). If you have resistor plugs, you need to check the alternator. An AM radio will pick up interference being generated from the motor too

i’d hate to give you more to do especially with a new boat…but is the 9.9 hooked up to the starting battery ? simple attempt to isolate the problem might be to unhook it and see if that solves the problem