I used the boat all weekend and the tach never gave a lick of trouble, oddly enough.
The hour meter has never worked on it. When I test drove it, the hour meter was blank (but the digital clock/sea and air temp meter also has an hour meter, which shows correctly). The hour meter on it now shows like 2228.2 on it (or something like that and doesn't seem to change), though the boat really has 341 hours according to the other gauge.
From some additional research online, it looks like this issue usually is the gauge itself crapping out. I plan on installing a Perfect Pass Stargazer setup in her this winter, so I'll just replace the tach with that unit and be done with it.