Hello from Humminbird! There are several things that can be done if you are getting interferance from your trolling motor.
Top three items to check when using a US2 Sonar
1) check the fuse in the trolling motor
2) loose US2 adapter near unit (make sure this connection is tight)
3) loose US2 connection in head of motor.(make sure this connection is tight)
We have several tips listed on our FAQ's (one being the below in regards to the US2 Sonar)
If you have a trolling motor that has Universal Sonar 2 you need to insure that the fuse in the head of your motor has not blown. A visual inspection will not suffice, you will need to check for continuity with a volt meter. If you do not know where the fuse is located in your trolling motor, you should be able to locate it in the exploded diagram of your trolling motor manual. This fuse is a 3-amp, mini automotive. If the fuse is blown, you should either
contact MinnKota Customer Service or one of their many
Authorized Service Centers across the US and Canada. Also make sure that the connections on the Universal Sonar Cable are properly tightened. If these connectors are not completely screwed in, noise can enter the unit from these openings.
Fuse location inside Motor Head
http://www.humminbird.com/uploadedIm...thumb_fuse.jpg
US2 Cable inside motor head
http://www.humminbird.com/uploadedIm...onnectors1.jpg
External US2 Cable the hooks up your unit adapter
[IMG]http://www.humminbird.com/uploadedIm...onnectors2.jpg[/IMG]
You can find additional troubleshooting suggestions at the below link:
http://www.humminbird.com/FAQ.aspx?ContentId=1849
Thank you
Deborah @ Humminbird