I used some PPG 2 part material to re-do the stripe (one between hull color and upper color)on mine many years ago and it is still great today--amazed me it hasn't come loose--
You can re-do the gel coat but you would need to pull engine and turn it upside down to do it right I would think. If the boat has many hours on it you might think about doing it all???? Looking at the rest do you think it was taken care of mechanically?
My 2 cents--