I am no expert at this
First, let me tell you that I have no expertise here, I only know what happened to me and what I was told. I sort of feel like, not being an expert, I probably should not have mentioned anything, but at least I can tell you what happened to me. OK, here is my story: I bought a 1998 Hunter 170 in 2001. It had a fairly large "spider" type crack near the rudder mount. It also had several small (maybe two inch) linear cracks in other, unrelated places, under the cargo cover, on the outer hull, etc. The guy who sold me the boat assured me that they were purely cosmetic. I called Hunter Composites looking for advice on filling the cracks, and wondering how to prevent future ones. The person I spoke to at Hunter Composites asked me to send pictures, he made sure that I could sail the boat in it's current condition. He told me to drill a 1/8" hole, 1/8" deep on the ends of every crack, this is to keep the cracks from spreading. I did not hear from him again for several months, to my surprise he called and told me that he would send a new hull the next time he was sending something in this direction. My new hull had some minor cosmetic dammage (there was a small area where the finish is dimpled like a golf ball). My guess is that they use hulls with minor blemishes for this type of thing. Now, this is my understanding based on my conversation with the guy from HC. The outer layer of the 1998 ACP hulls was made of a different formula of plastic than what had been done before. More of the 1998 hulls crack than previous years. He said not all of them crack, but the ones that do seem to crack a lot. They went back to the old formula in 1999. I do not know what percent we are talking about, perhaps a small percentage, but enough that they noticed, and switched back. I also learned from the guy at HC that yes the cracks really were cosmetic, they could have been filled and it would not have hurt the boat's performance, but he believed that it was reasonably likely the boat would have cracked elsewhere, and it would have been a constant headache. Also, he says that he believes most cracks on these boats are caused by tight fitting, dark, winter covers - that is - thermal expansion when the spring sun hits the dark cover. This may not be the problem in Corpus Christi that it is in Ann Arbor.Bottom line is that if I were you I would not hesitate about this boat for a couple of reasons; If it hasn't cracked by now I don't see any reason to think it would. You probably don't get the freeze thaw cycles we get here with your boat under piles of snow and ice for months at a time. Lastly and most importantly, when I had a problem Hunter stood behind their product. hope it helped. John