My Humminbird depth finder recently quit working. When my engine is running it no longer can find the bottom. It barely works at an idle, and works fine after I shut off my engine. Its set up with a through the hull transducer. Worked fine for 2 years and I havnt noticed that the transducer has gotten loose. I moved my power cable to my trolling motor battery to maybe eliminate electrical noise. Am I on the right track or is it just time to buy another depth finder? Any help would be greatly appreciated.