Pine sap, and some other conifer saps, will tend to stain the gelcoat on fiberglass, and will raise welts in clearcoat. I got my car under my brother's spruce tree for a few days, within four months after I bought it new. Three years of washing, polishing and waxing have not yet rubbed out the little welts left behind.
Used to be worse before clearcoat, sap left on long enough would lift the paint. These saps contain small amounts of some organic chemicals used in paint thinners. Turpentine used to be distilled from pine tars.
Repairing the paint will likely cost more than trying to clean the fiberglass.
