There are tons of reasons for crazing or cracking in gelcoat. To name a few, too much gelcoat thickness (which is usually a problem of older boats - especially with ortholalic gelcoats), or air in the lamination (often found on inside corners or from non-vacuum-bagged layups), or from stress in high load areas, or from fasteners, or from moisture getting into core material (usually through uncalled hardware), or from compression damage from impact, or from bad gelcoats that are brittle (which is a problem some manufacturers hav experienced much to their dismay), or from boat manufacturer screw ups by not properly sealing off underwater hardware in cored hulls), or I have seen it on boats that winter in subfreezing parts of the country. You will not find a dry older boat. But, you can find boats that don't have alarming, high levels of moisture. The best way to find problems is to have a good moisture meter and someone who knows how to use it. However, you can take a hammer and tap on decks and hulls and listen for a solid crack, or a thud. A thud usually suggests moisture and core deterioration. If you walk on the deck and it is spongy underfoot, that is not a good sign. If the cockpit floor is wet and you can move the pedestal steering back and forth, then you have a problem. Whatever the reason, it is fixable. It just depends on the value of the boat, its age and whether or not you should pass on it, or the repair is worth the cost because the boat is otherwise a good boat with value. If you have an old boat that has a bunch cracks in it, but no moisture problems, then it might not be worth spending money to fix it unless you are handy and have the time tackle the job knowing that you won't increase the value much because of it's age, unless it is a valuable classic. A surveyor can help with those questions. I have seen some pretty high quality and expensive boats with very small gelcoat crazing that have no moisture issues. They can be fixed, but is it worth it if it is merely cosmetic and not so easy to see? However, there are some makes out there that are known for hideous crazing, but otherwise are great, well found, good quality boats. If you own one and then find yourself with a boat with developing cracks that are hideous to look at, that is an unfortunate thing and when you sell it you will take a hit and in many cases it isn't worth the cost to fix. Bill out.