The hour meters that are built into the Gaffrig tachs on my 1999 353 with HP 500's have not worked since I got the boat earlier this year. One of my tachs may be reading low but thats another problem and I have not confirmed for sure with an engine computer. On the other end I found a pigtail wire by the distributor that is capped off but it appears to be like that from the factory. My understanding is the hour meter wiring is pretty simple just being fed by an ignition lead and having a ground. Since the tachs are working and all the wiring in the dash is intact I'm at a loss. Could there be an inline fuse? Any suggestions?

Sounds like you have two bad guages..... If they are seeing ignition then they should be working.

Correct - I checked the hour meter terminals on the old tachs and they were both getting juice so I threw in 2 new tachs last week. Livorsi still had a few left that are an exact match (except for saying Livorsi instead of Gaffrig). Took all of 15 minutes and hour meters ae now working!