If more than 1 bulb is involved in the blackout chances are it is a blown fuse. Or - if you're in a high humidity area - a corroded wire or terminal. This would not be affected by the number of hours on the
engine anyway but by the moisture level in the air.
On my first
boat I had the
RPM gauge acting up - one day it would
work, another day it would not. Took the panel out, turned out to be a corroded terminal which was not properly sealed.