boiled is the past tense of "to boil" and boiling is the ACTION of bringing something to a boil (defined as bringing a liquid to a temperature at which it bubbles and turns to vapor). Example: I just boiled water to make pasta for dinner. The water is boiling and ready for the noodles to be cooked. I hope this helps!

"boiled" means finished action while "boiling" means action in process the correct variant "The water would be boiling hot"

"The water was boiling hot." (where 'boiling' is an adjective) = The water was really, really, really hot. "The water was boiled hot." (where 'boiled' is a verb.) -- Sounds strange because, by definition, boiled water is hot. "The water was boiled." sounds more natural.