The SONAR signal has been deteriorating on our Navnet 3D equipped Safeboat over the past year. Looking at the transducer, it appears to be a brass through-hull model. It is mounted on a flat plate on the transom, and is in contact with our alkaline lake water 24/7. I have put a great deal of effort into tuning the SONAR settings, with no results. I'm thinking the transducer may not be designed to be submerged constantly. I'm thinking about switching the transducer for an Airmar transom-mount model. Am I on the right track here, or is there something else i should do first?