I posted this in the Boats Forum but have not had any response so I will try here. I have a 2003 Yamaha 150 OX66 and the last time I took boat out my speedometer stuck at 35mph. Yesterday I was out and all the speedometer had on it was a - (dash) All other functions of the display worked. Is there a pick up or port that could be plugged and if so what is the best way to clean?