Jaws: Why DOES Quint say 'I'll never put on a life jacket again"?

There is some point in the film when the Orca becomes the Pequod.

I assumed he did because Brody the entire time is telling him to slow down because he’s burning out the motors and Quint seems to accelerate harder once Brody tells him that.

That, I think, was just crusty stubbornness in the face of an idiot landlubber telling him what to do with his own boat, rather than a deliberate plan to destroy the engine.

Yeah, by that point Quint was just caught up in the madness of combat.

It was Hooper telling him to slow down, not Brody. Which was worse; he had some respect for Brody as a police officer, but there was no way he was going to do anything Hooper told him to do.

boatswain’s mate

Yeah, the radio…the engines, just him being a ‘dont tell me what to do’ dick.

Was cool seeing them all try and work together at the end though. Today, they’d stick some kind of stinger onto the end. Rather then say ‘what day is it’?..it’d be .“Should we send someone to retreive what’s left?”…“Fuck that guy”. (Audience roars)

Which would’ve been handy because they probably did need a larger vessel of some kind.

As mentioned upthread, I have no doubt the “no life jacket” line was to emphasize that the Indianapolis experience was so traumatic, that drowning would be preferable to enduring that again. Quint broke the radio because he was on a focused, manic mission to kill the shark and he did not want any interference or embarrassing rescue to interfere with that mission. I don’t believe he sabotaged the motor though. He wanted to bring the shark ashore for bragging rights (and collect the reward). No other explanations fit the character’s psychology or make cinematic sense.