There are several boats which have that seam--including the C Dory 25 which has a "hatch" which can be removed to change out fuel tank.
I used 3m 4000. It should not yellow, and can be removed if necessary. Usually C Dory used a Bostec compound. It can be removed with the bent back handle of a file and judicious use of a heat gun. Then there are various solvents such as lacquer thinner. (I keep a selection of solvents including MEK, alcohol, lacquer thinner, acetone, etc on hand.