I have a 2003 190 Bay also, and the Faria gauges that came with it have fogged up since day one. When they fog up now I just turn on the navigation lights until the heat from the light within the gauge clears them up. I gather they are not the best intruments around and I was told by the service manager where I bought my boat that I would probably want to upgrade to Yamaha gauges when the Farias eventually failed. Anyway, the tach began to stick last summer and I would have to tap it to free it up. This spring when I took the boat out the first time it was frozen at 3000 rpm and no amount of tapping on it would make it work. While the gauges may not be the best they do have a pretty good warranty policy. I took the old tach out, mailed it to them, and received a brand new one in about 10 days. This policy hold for the first 3 years that you own it, over that they will replace it for around $26, a speedo for about $13, that is if it's the instrument that has failed and not some other reason for them not to work. This is the link to the Faria website. Click on their link for warranty instructions for more info.
http://www.faria-instruments.com/