Has anyone replaced the original tach with a Teleflex Marine Tach/Hourmeter Model 82430P? If so, how did it work out? I would like to do this so that I can have an engine hour meter in the face of the tach. It appears that all I need to know is the take-off ratio of the pulse sending unit in order to calibrate the instrument. I can't find that information in the manuals for the boat or the engine and I can't find it on the Hunter or Yanmar sites. Does anyone know what the take-off ratio for the sending unit on my 2GM20F might be? Phillip Silent Dancer