I have Lowrance 113 C HD and when get below about .60 or .50 MPH it stops showing any MPH and just shows .00. I have seen other units show as low as .15 or .20. Can someone tell me how to correct this problem or is it just what it is supposed to do. Drift fish on Lake Mountrie and would like to see the speed when wind is less than 15 MPH. Some of you GPS guru set me straight please. Thanks guys in advance.