Drake Hogestyn, who played John Black, the sturdy and fiercely loyal character who by turns was a spy, private investigator and mercenary, for nearly 40 years on the long-running soap opera “Days of Our Lives,” died on Saturday, a day shy of his 71st birthday.

Mr. Hogestyn had pancreatic cancer, according to a statement from his family shared by the show. He died in Los Angeles, according to a publicist for the show, Andrea McKinnon.

In 1986, Mr. Hogestyn first appeared on “Days of Our Lives,” which premiered in 1965 on NBC and follows various characters in the fictional Midwestern town of Salem. For a few years, he played another character, Roman Brady, but came to be known best for his role as John Black.

Mr. Hogestyn appeared in more than 4,200 episodes of the soap opera and became a fan favorite for his portrayal as the rugged, raspy-voiced and often heroic character who had the skills of an intelligence agent, a police officer and a private investigator.

The character was also known for being married to Dr. Marlena Evans, a psychiatrist and the town’s de facto matriarch, played by Deidre Hall. In 2005, the actors won a Soap Opera Digest Award for Favorite Couple.

“It’s, like, I’ll always love her,” Mr. Hogestyn said, at a gathering for the show’s fans in 2004, of the characters’ enduring romance.