If the stress cracks are minor, I would say leave them alone. As a glass boat gets older the gelcoat will develope stress cracks. To define "minor", these are hairline cracks in the gelcoat.....they do not extend down into the fiberglass structure. If the cracks are larger you can clean them out, fill with MarineTex, sand level and paint with matching auto "touch-up" paint. An important thing is to keep the boat covered in the winter so water dosen't get into and under the gelcoat and freeze.
