Two years is about right
You say the boat was bottom painted in 1998. Alot of people don't get two years on abative paint like CSC, and often only one year if the bottom was cleaned monthly. Micron CSC wears off and disappears over time, and some spots may have been applied thinner to begin with. It's 2001, and "painted in 1998" sounds like a advertisement for Interlux for pete's sake. When you repaint with the minimum three coats, paint the first coat in a different color than the other two. When the "signal" or last coat begins to appear you will know exactly how much coating remains. As far as removing the barnacles, a good pressure washer will blow them off, leaving just the "foot" of the critter behind. If the yard has a really good pressure washer, even those are gone too. A different story if the bottom is crusted over completely, then a hoe-like scraper is used, then it can be pressure washed. You describe a few scattered ones or areas of them, however.