Towards the end of last season the depth gauge on my H34 went goofy. When we pulled the boat out in November there were some barnacles on the sensor. I got these off with a razor blade although it was harder than I thought and there's still some residue. I tested it and it reads 3'6. The sensor is actually about 4'2 above the ground but the ground surface is irregular and there's grass and weeds and whatnot. I've had the boat for 9 years and this never happened before. How should I clean and protect the sensor? Can you scrape or wire brush it? I know you're not supposed to put bottom paint on them but I use a clear coat on my shaft and prop that helps some. I think it's made by Pettit. What do you think?