Rod Taylor and Sam Elliot played Travis in Darker Than Amber and The Empty Copper Sea. Neither actor succeeded.
For one reason Travis is 6’4”, and having a shorter actor just does not make it . ( As this is being written there is a strong rumor that Leonardo DiCaprio will be filming a Travis story. But rumors like this surface every couple of years it seems. Don't pop the corn just yet.
If he were alive and at a right age Sterling Hayden would have fit the bill perfectly. He was 6’5” and had a strong sailing background, and a look at early Hollywood "stills" of him showed he had the looks as well.
Read Hayden's book: The Wanderer and you know what the water meant to him. Very much JDM and Travis.
Oh yeah, one more thing: (from Wikipedia)
Hayden, as OSS agent John Hamilton: his World War II service included running guns through German lines to the Yugoslav partisans and parachuting into fascist Croatia. Hayden, who also participated in the Naples-Foggia campaign and established air crew rescue teams in enemy-occupied territory, became a first lieutenant on September 13, 1944, and a captain on February 14, 1945. He won the Silver Star (for gallantry in action in the Balkans and Mediterranean; "Lt. Hamilton displayed great courage in making hazardous sea voyages in enemy-infested waters and reconnaissance through enemy-held areas"), a Bronze Arrowhead device for parachuting behind enemy lines, and a commendation from Yugoslavia's Marshal Tito. He left active duty on December 24, 1945.
Now, how much more would one want to qualify an actor, and real life hero, to play Travis in the movies??