The brilliant news is that generally speaking the older hatches are straight forward to remove. Newer Lewmar (LP/MP) units can be another story (RS - I'll do a blog post on this).
As with the windows, use a piece of masking tape to identify the location of the hatch. Take photos with your phone so you can remember how it was before.
Unless it is necessary (or prudent), do not remove the base plate (or ring) that is attached to the deck of your boat. This should have a good seal, and if it is removed, will require cleaning and resealing. Most hatch tops or lids can be removed by either knocking out the hinge pin with a mallet (not Rollstop please) and parallel punch or unscrewing the hinges from the top or base.
If you are sending the hatch to Eagle Boat Windows for repair, please leave all the handles and hinges attached as we will service and reseal them.
Refitting the hatch should be straight forward and opposite of the above sequence. Please be aware that if a new seal has been fitted, the hatch will feel very stiff/tight on fastening down.
Now some Model specific guidance...
Both have what Lewmar describes as a 'knuckle' type hinge, where a pin rubs against a cast 'knuckle' to open/hold the lid in position. Official hinge replacement kits for Superhatch models are long gone and there are generally very limited (ie eBay) sources for Rollstop. Having said that custom made replacements for Superhatch are listed on the US site Hatchmasters.com).
Only disassemble these hinges as a last resort. The best option is to remove the lower hinge part from the base plate (so keeping the whole hinge together). This may be screwed down (easy) or bolted. If the latter, fine if the nuts are captive but a pain if not as you'll need to take the head lining down to gain access.
On Rollstop hatches size 44 and below Lewmar added a rivet to the hinge/base join to hold them together during transit. As a result, you will either need to drill the rivet out to release the hinge or remove the whole hatch, base and all. Given the age (Rollstop stopped in 1992) the latter option may not be a bad thing.
These have pinned hinges. The pins are stainless but have a black anti-corrosive coating so even though within the Aluminium hinge will generally come out easily, particularly if you apply a heat gun to the hinge and some releasing fluid to the pin. We have some Lewmar notes on this showing how.
Lewmar Coastline, Trimline and Trimport
I don't have any specific guidance yet but suspect similar to Ocean
Lewmar Low Profile and Medium Profile
I'll do a blog post on this at some point! The hatches with 'other' support ie a stay or friction arm have plain hinges which comprise two outward slotting alloy bearers which are held in position by a central rod and a spacing clip. These are relatively easy to remove.
The smaller units which rely on friction within the hinge for support are less easy, but doable with the correct approach/tools. Essentially, instead of the rod and spacer above there is a nut and bolt arrangement, each with a small hole into which a small allen key can be inserted. By unscrewing the nut/bolt the bearers are forced out increasing the friction. When manufactured, this tension is locked with loktite 243. For removal I advise the following: get a (very) small pair of mole grips. Place a 2mm allen key into whichever side has the hole which goes all the way through (for most leverage). Attach the mole grips to the other side. Use a heat gun to release the loktite and undo. Once the nut/bolt elements are screwed together (clockwise) they can be removed and the bearers will move inward and release.
Other hatch notes will be added in due course.....