[apex2000]

What is "growing grim about the mouth"?
What is "in my soul"?
What does the author mean by saying "pausing before the coffin warehouses ...."?
What does "hypos" mean? What is "knocking people's hats off"?
What is "account it high time"?

The first three are all about his feelings of depression or thoughts of death. They mean that when he is 'down', or feeling low, or fed up with life, even getting desperate because he so dislikes whatever state (this could be of mind or position) he is in.
'hypos' is probably a contraction of, say, hyperactivity or 'hyper' thoughts so that he does something quite unusual such as literally knocking people's hats off (their heads).
The final one refers to him deciding that it is about time that he changed whatever he is doing and get back to sea. There he will feel better, be of more use either to himself or others, be where he feels at ease within himself.