Well it’s the whole bottom of the boat where it was sitting in the lake. Will the hull cleaner or toilet bowl cleaner hurt the carpet on the bunks?
I did the Star Brite hull cleaner like others have suggested at the car wash. Spray it on, let it soak then use the foam brush, then rinse. It worked great on my white hull and did not affect the carpet on the trailer. I have an painted trailer and it was not affected by it either but I did rinse everything off after using the foam brush to scrub the bottom. If it does not come off the first time do it a second time. It works very well.
I have never tried the toilet bowl cleaner.