I have depth and speed guages on my boat , both with knobs then tend to slip and just spin around. They are both made by "Stowe Marine equipment Inc. " Depth is called the "Navsounder" and the Speedo is called the "Navigator 1". I have the manuals but have been unsuccessful thus far in contacting either Stowe (UK company) or the local (USA) contact they listed. I wish to purchase new covers for them (both absent) and also get new knobs or possible have them factory serviced. My boat is a Moorings M510 which was built in France in 1993 . All leads and suggestions appreciated. John