I live on the gulf coast where humidity is high. I stained my fiberglass door with Zar stain and sealed with Spar Urethane. It looked great. Over the winter the door was covered with mold.
I had to remove the urethane and restain. Now I’m afraid to put more urethane on the door because I won’t be able to clean the mold. Every time I clean the mold off some of the stain gets removed. Any suggestions?
How many coats of the clear finish did you use? You should have at least 2 coats for good protection, 3 thin coats is better. The stain shouldn't be removed if there is enough clear finish protecting it.
Suggest a very good cleaning, restain if needed and clear coating with several thin coats.
You could try a tougher clear coat. Use McCloskey's Man-O-War Marine Spar Varnish, very tough and UV resistant when fully cured.