When I repower a machine or just replace the hourmeter, I mark the former machine time on the area near the hourmeter, for example, on my machine the hourmeter display would only show correct time when I pushed on a part of the face of the hourmeter. I replaced the hourmeter and marked the frame with " 350 +" next to the hourmeter.
I have also wired that hourmeter to a separate 12 volt battery and connected a low amp output charger to the battery as the hourmeter time advanced to the point where I wanted it to be. Bear in mind that it takes 7 full days to put 168 hours on an hourmeter, so this process can take some time during which you need to monitor the time when it gets close to the specific hours that you want indicated on the meter.
Mad Mackie in CT