i was just wondering what keel bolts with lot of use look like and what new keel bolts look like and keel bolts that are junk look like. just want to get a idea of what condition they are in. ill post a pic tomorrow of mine.
What you describe sounds like the way the keel is mounted on a Thunderbird - essentially large flathead machine screws upside down through the flange.I'm pretty sure that the Coronado 27 has an iron keel with a flanged root. As such, replacing the keel bolts is very different from doing so on a boat with a lead keel.
The root of the keel sits in a "shoe" molded into the underside of the hull, and the bolts probably have countersunk heads. Remove/replace one bolt at a time. To replace the bolts you get the nuts off (use a nut splitter, cut the nut with a cut-off wheel, or just cut the bolt), then hammer the bolt from inside the boat until the head makes enough of a "pimple" in the fairing so you can tell where it is from the outside. Cut/dig/remove enough fairing to make the head of the bolt visible from the outside (or just hammer it all the way through), and hammer the bolt the rest of the way out. (Did I mention that the boat should be out of the water?). Now, take that bolt to someone with an assortment of iron pan-head bolts and match it as close as you can. Don't bother trying to figure out the size until you've removed a sample bolt, you'll never get the length or head right. You should probably get iron bolts, nuts, and washers to prevent galvanic problems. Put it back together with lots of Dolphinite bedding compound, and torque it down to about 50 ft-lbs, then start on the next bolt. When they're all changed, torque all the bolts to the max recommended for the diameter bolt you are using (ask for the specs when you buy the bolts). When everything is tight you can either refair the keel root, or (if you have a real masochistic streak) take the opportunity to strip the keel completely (old bottom paint, fairing, Bondo, whatever), prime it with an anti-corrosive paint/epoxy, refair it nice and pretty, and repaint it with antifouling.
Take lots of pics during the process, because hen you're done you can post them and then you'll be the SailNet guru when it comes to replacing the bolts in this sort of keel.