Indeed, the name of Cap'n Crunch Crunch Berries cereal was called Horatio Magellan until 2007.
In May 2007 Cap'n Crunch's full name was revealed as Captain Horatio Magellan Crunch. It was also revealed on Cap'n Crunch's own baseball card (Cap'n Crunch's Home Run Crunch cereal) that he was "young" in 1963 but according to the picture, old enough to have white hair and mustache, reports Wikipedia.
Daws Butler was the original voice of the Cap’n and continued in the role until his death in 1988. Therefore, the ads were titled Captain Horatio Magellan Crunch.
"In modern TV ads Cap’n Crunch is often seen riding his ship through a wall as the whistle blares. He often comes in the middle of a predicament and uses his cereal to solve the problem at hand by “Crunch-a-tizing” it. Another reference to the cereal’s crunchiness, a regular theme used to feature Cap’n Crunch battling off the evil “Soggies” who attempted to “sog out” the taste of his cereal. In a recent ad, Jean LaFoote returns, this time trying to steal the Captain's cereal recipe.
"Cap’n Crunch was the most popular children's cereal from 1965–1971 when Post released its fruit-flavored crispy rice cereal known as Fruity Pebbles. It took six years for Crunch to dominate the segment again, releasing a new flavor of the crunch berry ingredient, grape."