I purchased a Garmin 541s for my new 215DC. It did not have a GPS when I bought it. When I started to try to run the transducer cable, I noticed a thru hull transducer was already mounted in the bilge. Trouble is, the connector looks like an old stereo plug. Just a single pin. Is there an adapter available. I looked at West Marine but couldnt find anything. Anybody ever run into this? Any ideas?