That isn't right. You are 100% sure that the transducer is a TM185M? The Airmar TID chip is what identifies itself to the sounder. The TM150M is a 300w transducer and the TM185M is a 1KW. I would not expect the unit to give very good deep water performance. Do you see the TM185M in the setup for doing a manual selection? If it is a TM185M then i recommend you see if you can swap to manual selection and pick the correct model.