In The Cay, how and why did Phillip's attitude change towards Timothy? What was the ultimate sacrifice that Timothy made for Phillip?

Phillip treated Timothy with disrespect. He demanded more of the water rations than was his share, refused to help set up shelter, and viewed Timothy with stereotypical disdain. He found Timothy's inability to read or write further reason to ignore his advice.

This begins to change when Timothy finally snaps and slaps him for his behavior. This seems to awaken some respect for Timothy, and he begins to see the value in his advice for survival and self-sufficiency.

Timothy's ultimate sacrifice comes when he shields Phillip from the worst of the effects of the hurricane, despite being stricken with malaria. Timothy ultimately dies from the injuries he received.