What would the hour meter measure?
Most if not all multi-function plotters have a total trip time and total 'moving' time counter. The difference between the two is that the trip time is the total time that the unit is powered up whereas the moving time or whatever it is called counts the elapsed time over a pre set speed. In other words, if you sit with the motors on but not moving faster than the trip speed, the 'moving' time will not increase.
Bottom line is that that counter doesn't really give you engine hours if that is what you want.
So.. what is it that you want to track?