Same problem with my Volvo MD22L
I doubt that you have a Volvo, but I had the same problem. Volvo replaced the entire tack/engine hour instrument under warrantee during the first year.Now, 5 years later, the same thing happened again, but is intermittent.I truly believe that there is a bad connection somewhere, but until it quits again AND I feel like troubleshooting instead of sailing, it won't get fixed.I log my engine hours each day, so I always know approximately what I have.I have observed that although the display is out, the hours keep counting. When the display comes back, the hours reflect the true value.My fuel gauge is also on the fritz and I judge the fuel level by counting engine hours. Having BOTH instruments quit is a PITA.Rich