This was never going to be simple, trust me…
Not only are the inserts which hold the frame sections together corroded by years of salty exposure, the hinges are likely to be difficult to remove and need replacement. Not quite as for the new units in the Lewmar videos!
Unsurprisingly there are a number of hinge variants so let’s start by understanding the differences.
Mk 1 or Mk 2?
To start with we have two variants which can be distinguished visually before disassembly. The older Mk1 has rollpins inserted either side of each hinge mount in the lid. It appears these pins are there to limit the movement of the plastic plug which holds one end of the hinge pin. On the Mk2 these are not there, but equally I suspect the hinge components are also of the later style as we will see. Note that any new spares will only be Mk2, but this is probably a good thing.
Type A or Type B Hinge Components
Then there are the hinge components. I’ll denote these Type A and B.
Type A - non-friction hinge
Type A, the most recent, features two alloy pistons which push outwards into slots in the base. A relatively thin plastic rod fits between these and a plastic cap clips over this to stop the pistons from sliding out of the base on each side. The alloy pistons have plastic cages to reduce friction/corrosion and have quite a large bearing surface being ~5mm in diameter.
This kit (see right) just allows the hinge to pivot. It does not provide any friction to hold the lid up, this function being performed by the friction lever(s).
These kits feature on all current/recent LP/MP hatches fitted with friction levers. Individual hinge kits (Type A) are available from Lewmar as a spare and contain parts for a pair of hinges (4 pistons etc), including new exterior plastic covers.
By default, when refurbishing any LP/MP fitted with friction levers we will install these Type A hinges if replacements are required.
Type B - friction hinge
Type B feature an expanding barrel nut/bolt which when screwed out to expand can introduce friction to the bearing surfaces. I say 'can' as on some larger hatches fitted with friction levers these are frankly unnecessary.
Where they are necessary is on the smaller LP units (size 00-41) which don't have friction levers. For these I suspect the older units (inc Mk1) will have bearing wedges where as newer will have the current alloy bearing pieces. I'm not convinced it's a simple Mk 1 vs Mk 2 thing as we've got some MP70 units which are Mk2 but still have the wedge version.
So I'm going to denote the Type B with wedges as Type Bw and The later version with alloy inserts as Type Ba. Simple.
Both versions feature a threaded stainless steel expander (think nut and bolt) with either
Type Bw - Pairs of opposing plastic wedges on each side with the outboard wedges having a central 2mm stainless pin and a plastic mount/plug which locates in the base on either side of the hinge. Effectively the 2mm pin is the bearing which unsurprisingly doesn’t last well, causing the hinges to become loose. The wedges on either side are compressed by the expander putting pressure on the plastic/lid frame bearing surface which creates the friction to hold the lid in position. When originally fitted, Lewmar apply Loctite to the thread to ensure the expander doesn’t become loose. All of this mechanism is covered by a grey plastic cover which clips over.
Type Ba - An alloy piston with a plastic end on each side. There are some other parts which probably allow this kit to be used on other products as well but theu are not necessary here. This kit is shown to the right and is available as a Lewmar spare. But see Lewmar update below...
Why is this important?
Type A hinges are straight forward to remove and can likely be reused. Type B hinges are painful to remove and unlikely to be reusable.
Update from Lewmar...
The Type Ba pack above shows four caps, four long bearings (with plastic cover) and two short bearings (alloy), plus the two expansion joints. Back in the distant past the LP and MP hinges had different caps. Now they don't, but they still put two sets in the bag so you get an extra pair, in spite of them all now being the same (!). Next, the short bearings are required for the smaller hatches up to size 20 where the actual hinge is shorter. This only applies to the LP as the MP range starts at Size 30. So if you have a MP or LP >= Size 30 you can discard these and just use the long bearings.
Note that the Type A hinges (above, non-friction) only come with the long bearings so are unsuitable for the smaller LP units.
As a rule, Lewmar say they use the friction hinges (Type B) on MP models and the non-friction (Type A) on LP models. They say the MP need the extra friction (in addition to the friction levers), but I'm not sure I buy this as the Ocean (which is heavier) has only the friction levers... But as the packs are virtually the same price you can decide.
Removal Instructions
Type A
remove the outer grey plastic cover – use a screwdriver from behind to lever up the lower edge. Do not try and lever off from the top as you will likely break the cover. Place aside for re-use.
between the lid alloy hinge sleeves you will see the black clip on cover holding the pistons in position. Using a screwdriver or similar lever this off, taking account it will probably ping off so be careful you don’t lose this.
next, remove the thinner (~2mm) plastic rod which fits into each of the pistons (onto which the above clip is clipped).
you should now be able to lever out each piston. You probably don’t need to completely remove these, just bring them inboard sufficient for the outboard ends to disengage from the sleeves in the base frame.
repeat for all hinges and remove the lid.
Type B
This is way more complex and as a result I've written a separate Blog article entitled - Lewmar Low/Medium Profile Hatches - Release Hinges. Click on this link to view.
If the hatch has friction levers, we’ll fit new Type A hinges during reassembly.
Take note before sending io your hatches
The astute amongst you will have realised that to fit a new acrylic and seal we need to split the lid frame sections and this can only be done when the lid is removed from the base.
Reading the above you will now appreciate this is often not a simple or quick job so if you send in hatches with lid and base still attached please understand when and why we will charge extra.
What about smaller hatches without friction levers?
These will have the friction hinge version (Type Bw or Type Ba). Lewmar do a slightly different hinge kit for these which includes a new expander but also uses the alloy pistons, a much better solution. This kit is shown for Type Ba above.
How much are hinge kits?
Hinge kits (either type) are approximately £55 + VAT per pair (ie replace two hinges).