Upgraded to Raymarine i50 speed/depth, i60 wind and p70 autopilot a few years ago. For the past two summers, over a period of several weeks, boat speed is not recognized (shows zero) which obviously impacts calculation/display of true wind. Happens mid-season with no warning. After several weeks, speed will be back and all instruments working normally. Pulled transducer, no obstruction. A nuisance more than anything else, but I'd like to find the reason/a solution.