It sets up the audience for the horror that is about to come. One of the best setups ever.
The underlying theme of Quint and his pending doom is brilliant. His lifelong vendetta against sharks is evident. He's abrasive, arrogant and cocky, but as the film progresses, we see his internal horrific fear of sharks come out more and more, until he eventually gives up and asks Hooper for help. He even breaks out the life jackets, because he knows that they're doomed.
I think he's also carried a tremendous amount of survivor's guilt with him all those years. He's dedicated his life to killing sharks, but I think on some level not too far down, he wants to suffer the same fate as all the crewmen who died in the water.
That's possible. He may have a death wish, which is why he hunts sharks for a living. He's Ahab, waiting for his white whale to come for him.
He pretty much f*cks everything up when he smashes the radio. And then blowing out the engines was the icing on the cake.
The book pushes the Quint/Ahab connection to the point where they die the exact same way (drowned after being caught in a rope attached to the whale/shark). Oops. Spoiler!