I just had some issues with a new HB and used the ring on the transducer cable for unit. Then I put a stripped wire under the hose clamp for the transducer, put another hose clamp on the shaft and tied in there with a wire ran from the negative side of the TM battery. (made all the metal parts on the TM common with the negative of the TM batter) I also put a wire between battery negatives but you can try it without first....bottom line is you are going to need to ground the TM. I also split up the transducer cable and power cable for the TM. I am working like a charm now