Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The answer to your question depends upon these points:
1. what (4-pin) transducer (by maker and model) are you using with the Garmin Echo 100 ?
2. (and/or:) what port on the Garmin Echo 100 is the 4-pin transducer hooked up to, please? or, what port type is it, or can you photograph the port and post the photo file to me?
With that info, I could answer your question. Use the Reply To Expert function to let me know. Thanks.