Marin began his career in his native Cuba, working as a groom and an exercise rider at the Oriental Park Racetrack, in Havana. In 1935, he signed on as the agent for Fernando Fernandez, and the rider was the Cuban champion for the next seven years. In 1943, the pair moved to Mexico City to compete at Hipodromo de Las Americas, and Fernandez led the nation's riders there for three years straight. When a riding contract for Mexican president Avila Camacho expired, the pair headed to the United States, where Fernandez became a leading rider on the East Coast circuit until 1953. Retiring that same year, Fernandez ranked seventh on the list of world's winningest riders, with 2,186 career wins.
For the next several years, Marin represented riding stars Don Brumfield and Manuel Ycaza, both future U.S. Racing Hall of Fame inductees, as well as "Milo" Valenzuela, with whom he won the 1958 Kentucky Derby and Preakness Stakes on Tim Tam, for Calumet Farm.
In 1960, Marin secured a riding contract for Panamanian champion Braulio Baeza, and represented him for the next four years. During this time together they won the 1963 Kentucky Derby aboard Chateaugay, and two Belmont Stakes. Baeza was elected to the U.S. Racing Hall of Fame in 1976.
In 1966, Marin began working for nineteen-year-old Laffit Pincay, Jr., who was elected to the U.S. Racing Hall of Fame less than nine years later, and who retired in 2003 as the world's winningest jockey.
Other well known riders that Marin worked for included Jorge Velasquez, Bobby Ussery, Angel Cordero, Jr. and Steve Cauthen, all U.S. Racing Hall of Fame inductees, as well as Eddie Belmonte, Alvaro Pineda, and Heliodoro Gustines.
In 1973, Marin told the Orange County Register "So far I have been fortunate. I have had almost every top rider in America, and I have won just about every major stake (race). I have no complaints."
He died December 1, 1988 in Arcadia, California, only several hours after the death of his first jockey and lifelong friend, Fernando Fernandez.