He joined his brother in America in 2002, and drove in Grand Am and the American Le Mans Series, winning 1 race in the LMP 675 class.

In 2006, he returned to Scuderia Ecosse for their effort in FIA GT as well as making assorted other appearances in high-profile sports car endurance races, including the 24 Hours of Daytona for SAMAX Motorsport.

In 2007, he signed a full-season deal to join his brother at Andretti Green Racing and to be the full-time driver for their new ALMS P2 class Acura entry with teammate Bryan Herta.

Both Franchitti brothers left the team after the 2007 season and while Dario went to NASCAR, Marino continued in the ALMS, switching to Dyson Racing's Porsche RS Spyder, partnering with Butch Leitzinger.

For 2012, Franchitti was confirmed as the first driver of the Highcroft Racing DeltaWing, which ran as the 56th and unclassified entrant in the 2012 24 Hours of Le Mans.

Marino and Dario Franchitti are also cousins of fellow Scottish racing driver Paul di Resta, and are friends off the track with Allan McNish.