I suppose you have all noticed that there is orange crud that is deposited onto the boats at BMC. I have an opinion about where it derives, but the purpose of this discussion is just to tell you a moderately inexpensive way to wash it off.
I have been asked about this by more than one owner and keep forgetting to share.
The expensive way is to use On & Off from West Marine (~$15.99/quart). Use 1/3 of a bottle to about 1 gallon of water. Brush in onto the orange. Wait 2 to 3 minutes. Hose it off. The orange will be gone.
Less expensive: Buy a gallon of Muriatic Acid at Lowes (hydrochloric acid). Dilute it 1 cup to 1 gallon water. Then follow the directions above for On & Off. i.e. yes you dilute it again: about 1/3 quart to 1 gallon of water. [Just be careful with the concentrated Muriatic when making the dilution at home. It is 10 Molar and will produce acid burns to you skin.]