I have been wiping & cleaning with a pressure washer using soap after every outing with my boat & the crud on the hull just kept getting darker & darker. I boat in the dirty Ohio river & I can see crud building up on the hull causing a bath ring around my boat. After winterizing I tried just about everything to clean but nothing worked, a buddy told me to use polishing compound & a drill with a bonnet on it to buff it off. Knowing that's abrasive I didn't want to start that. I had tried the Star Bright hull polish but that wouldn't cut the crud. I talked to a woman in Walmart that said she & he husband have a boat & she buys this for her husband to use. This stuff is wonderful, just spray let it cut the crud & wipe it off. This stuff is so great everyone needs to know about it.
"The Works" toilet bowl cleaner, liquid not gel, has the same active ingredient and cost $2.99. Works exactly the same.
That's an acid based hull cleaner, it either has Oxalic or Muriatic acid in it - toxic stuff, don't get it on your skin, trailer and try not to breath the fumes. However, when it comes removing the brown stains on a white hull, that's the only thing that will really do it.
Likewise. When I bought my 98 290 DA although it was clean the rust stain was a pain in the butt until I discovered the magical properties of Rust-Aid spray from Goof Off. While swimming I can just spray and watch it disappear in front of my eyes. No scrubbing at all. Magic I tell you.
No telling how much money I have spent over 40+ years on various products marketed as "hull cleaners", that performed poorly. I now use Barkeepers Friend for the bathtub ring. Heard about it on this site from @carterchapman . Cheap ($3) and extremely effective.