I had to get my speedo repaired 2 years ago in my 1999 Mantaray and Was very surprised to find it was cable drive not electronic, the speedo was under reading by 20mph. The fault was due to a cracked outer casing that was allowing the cable drive to float around in the housing at the back of the casing. The fault was fixed by a rebuild using a replacement casing. It is the Standard Smiths unit