That is not crazing. Crazing makes the gelcoat look almost like aligator skin or a dried up lake bed. Those are stress cracks. To fix the crack use a very small drill bit and drill a hole through the crack at each end to prevent further spread. Then open the crack with a dremel and fill. Before you go through all that trouble you need to determine how to reinforce the area or the cracks will come back. As said earlier the bolt may have been overtightened. My recomendation would be fix the overstress/under built issue then repair as described above.