I'm surprised no one has responded yet. When re-caulking anything the most important things are to clean both surfaces of the old caulk and any dirt first and to use the proper caulk.
Carefully remove the hatch. Once all the screws are out use a putty knife (,plastic if you've got one) to gently break the seal of the old caulk all the way around. Once the hatch is loose you can (again, gently) lift the hatch off the deck. Clean the old caulk off both surfaces with your plastic putty knife followed by wiping it down with a cleaning solvent... I prefer Acetone but don't use it on any rubber, vinyl or clear/smoked plastic.
Finally, you are ready to re-caulk and replace. Now, here's where everyone has an opinion, including me. Do not under any circumstances use 3M 5200 for this job and you'll thank me later. It's an adhesive that will have you kicking yourself if you ever have the need to remove the hatch again. 3M 4200 is ok but I prefer the Life Caulk products. Make sure you use a matching color or clear and only caulk on one of the mating surfaces. Now, here's another opinion and I'm not certain it makes a difference but it seems logical so I've always done it. After caulking, place the hatch in it's proper location and snug the screws down in a cross pattern so the hatch settles in evenly. Don't tighten it all the way down because you squeeze out most of the caulk. Wait about 24 hours so the caulk dries to form a nice gasket then tighten everything down.
Good luck
