Born in Olite, Navarre, Marañón arrived in the Real Madrid youth system at the age of 19, making his professional debuts with Ontinyent CF in Segunda División, on loan (a similar move occurred in the following season with Sporting de Gijón).

He joined Real's first team permanently in 1970, but never imposed himself at the club during his four-year spell, appearing in a maximum of 19 La Liga games in the 1973–74 campaign.

After two slow seasons he would never score in single digits again, also playing European competition with the Catalans, gaining captaincy and reaching the national side.

[2] Capping off his best season at Espanyol – 22 goals, good enough for joint-second behind Valencia CF's Mario Kempes, as the team nearly qualified for Europe – Marañón made his debut for Spain, appearing in a 1–1 friendly with Hungary in Alicante on 27 March 1977.

Subsequently, he was picked for the squad for the 1978 FIFA World Cup but did not play in the finals, earning a total of four caps in roughly one year.