MK20 UL different models

[jale]

Hi.
I got lucky enough to be able to put my hands on three Scubapro UL regulators: 2 MK20 and one MK18, the three in INT.
I am starting to overhaul them and to change them to DIN.
I realized that the two MK20 have different colors. One being matte black and the second shinny grey!
I didn't know there were different styles of UL!
Anybody has info about that?
Thanks

 

[Mobulai]

Very nice find, congrats

All my 20ULs are the shiny versions ( left on your photos), my 18ULs are matte
IDK what (or if it does even) it indicates

Which DIN retainers are you using? I’m assuming the ALU ones are NLA

I also have a few 18ULs that I want to convert from INT to DIN at some point (they’re never in water so far)

 

[jale]

Just normal DIN. Would be a kind of hybrid version being well aware that the two metals are not "friendly" to each other in sea environment

 

[Mobulai]

Just normal DIN. Would be a kind of hybrid version being well aware that the two metals are not "friendly" to each other in sea environment

Same plan, some tiny part of me was hoping you’d say you have a super secret source for the UL ones

I guess we both have to take off the retainer after each dive season

 

[Eric Sedletzky]

What are "UL" ones?

 

[Mobulai]

Ultra Light, they were made out of anodized Aluminum

They eventually were cut from the SP lineups in favor of titanium alloy (TA/STA) then Ti

 

[jale]

Same plan, some tiny part of me was hoping you’d say you have a super secret source for the UL ones

I guess we both have to take off the retainer after each dive season

No NLA nor NOS. Sad indeed

 

[axxel57]

The Mk20 Ultra Light (UL) came, I think, for 1997 on the market.

The problem with them was (and is) that the body was very sensitive to corrosion, especially when using it in salt water.

One had to soak and clean it thoroughly after each dive to prevent that parts of the aluminum body was ‘eaten’ by salt residues (mostly at the hose ports), which made the bodies quite ugly and sometimes the damage was so bad that the turret or the main body had to be replaced.

Another problem was that often owners didn’t change the special washers that came together with the HP and LP Hoses, to the new hoses they installed.

That means that you had a direct brass aluminum contact which should be avoided similar you don’t want to have direct contact between your brass tank valve and your AL Tank threads.

Anyway, in 2001, just short before the MK25 was implemented, SP changed the form of the turret for all new MK20 models, and tried a new, more resistible coating on the MK20 UL.

The new coating was better than the old one, but unfortunately not much, so finally SP gave up their MK20 UL 1st.

Some hints concerning the DIN connectors for the MK20 UL.

First, if you didn’t have problems removing the INT Screw, lucky you.

If you find an old original MK20 UL DIN ( I have about eight), the thrill in the beginning is the question if you are still able to loosen the DIN connector. Mostly it’s much more easy to remove the UL Retainer Screw for the Yoke than to remove the DIN Connector Screw.

Those 1sts are mostly almost 30 years old and often they have been laying around for decades, so the lube is dry and AL is not as strong as brass. So the removal can be very time consuming.

Even worse when a brass DIN Connector was installed without the appropriate lube like Molykote 111.

Removing such a brass connector can render the body useless, because the threads have disintegrated ( sorry, if my technical terminology is not exact).

To avoid too much stress on the body and the threads, I tighten the DIN Connectors with max 27Nm, but that’ just my personal way doing it.

So, if you don’t find a AL DIN Connector and use a brass one, be aware of these ‘problems’ that might occur.

If you find a MK20 UL in the Bay, look for the new turret, chances are that it is in quite better shape also inside. I’m always willing to pay more money for it…..

BTW, I like my MK20 ULs a lot, using them when travelling, but they are ‘Princesses’ and cost extra attention…..

 

[jale]

Thanks Axxel for all these details.
I didn't know the UL stayed in production for 4 years (1997 to 2001?). I thought it was shorter.
Beside MK20 and 18, has the UL been used with other models?
About turret, are the one in the pictures new or old? Is the grey one a newish model compared to the matte one?
Yes, indeed, these are to be treated as Princess

 

[Mobulai]

I think around 2000 the turret design changed across all models (This might be a different issue tho, IDK) — a „scallop“ was added
I have no example from the ULs myself but I believe that shows it (in a completely different context)

Sealing a Mk25 started to look like diminishing returns.... I never got an answer sorted that I'm truly happy with. On the other hand, the Mk20 boot copy seems to work just fine.... and I understand that a Mk20 can be upgraded to Mk25 with the piston and seat retainer. I think early 25's also had the same body as the 20. Only issue that's been brought to my attention about those is that the UL scalloped turret doesn't properly retain the upper edge of the boot, but I've made a retainer ring in TPE that pops on over the turret to achieve the same result. I don't have a picture of it installed (a Mk10 is the newest reg I own myself), but here's a picture of two Mk20 turrets, one scalloped (left hand) and one earlier design, to show what I'm talking about.
View attachment 793855
If you need a Mk20 boot (and or adapter ring for the scalloped turret) let me know.

Respectfully,

James