A hinge assembly for a hatch cover of a watercraft includes a hinge arm having a substantially J-shaped configuration and made of an extruded material, a deck mounting bracket for connecting the hinge arm to a deck of the watercraft, a hatch cover mounting bracket for connecting the hinge arm to a hatch cover of the watercraft, a hinge shaft connecting the hinge arm to the deck mounting bracket, and at least one mounting member connecting the hinge arm to the hatch cover mounting bracket. The hinge arm has a width dimension extending in a longitudinal direction of the hinge shaft that is greater than a thickness dimension extending in a direction perpendicular to the longitudinal direction of the hinge shaft.