If the gasket is leaking, you can try adjusting the hatch closure cams. On eith side the lever that dogs the hatch closed has an adjustable cam on the lever. You will need to tighten them in very small increments,
On a 20 year old boat, it is more likely that the hatch is leaking around the seal to the deck. The hatch needs to be carefully removed from the deck, the hatch and gelcoat on the deck cleaned and t he hatch rebedded to the deck.
A word or caution here: The deck on the 440DA is fully cored and if the hatches have been leaking a while, there is a good chance that the core between the deck and headliner is wet and has begin to rot. If that is the case, the coring needs to be removed and the wet area dried out and filled with epoxy of new coring. Removing t he hatch and repairing the core isn't a D-I-Y job unless you have done it before. This one may be best left to the professionals.