Scubapro Mk2 with s550 and R380 - Nitrox

[rhwestfall]

There's a bit more to it. The added bulk of a 2 gauge console is cumbersome while diving, and the need for a redundant depth gauge is really very low in recreational diving. If you are diving with a buddy, you simply use his depth data in a pinch if your computer were to fail during a dive. Also, you will want to check depth/time pretty frequently, and air pressure only occasionally once you get some dive experience. This means it's very convenient to have the depth/time info on your wrist and you can clip the SPG on your BC for much of the dive. I think the most convenient is a bare SPG, no boot, on a 24" hose with a bolt snap attached. The boot also tends to collect water; they're not really waterproof and sea water gets trapped in them. This can be pretty corrosive to anything metal in the console.

yet folks are going to do what they are wanting to do.... My wife will not give up her console, so its easier to just let her do it that way. Just make sure its stowed/retained in a decent manner, and carry on. There really isn't the "downside" folks go on and on and on about.... maybe in time......

 

[gilbertpaul]

yet folks are going to do what they are wanting to do.... My wife will not give up her console, so its easier to just let her do it that way. Just make sure its stowed/retained in a decent manner, and carry on. There really isn't the "downside" folks go on and on and on about.... maybe in time......

Hi all

me again ( feeling like an idiot !)

the regs have arrived and looking at the service paperwork ( handwriting not great) I now believe the first stage to be a mk20. Not a mk2

there are no markings on the 1st stage other than the serial number

so questions again- is this a better pairing with the s550 and r380 ?

i wanted the mk2 as they are so reliable so not sure to keep the mk20 ?

would service costs etc be similar? Are they as reliable ?

any downsides , or have I ended up with a better deal ?

many thanks

paul

 

[DA Aquamaster]

The Mk 20 is a solid regulator and an excellent performer. The Mk 15, Mk 20 and Mk 25 are a continual evolution of the same design. The Mk 20 had a different design for the piston stem bushing system that was easier to service, and incorporated a series of small improvements over the years. The changes were gradual and the first Mk 25 was identical to the last Mk 20 that came off the production line, with the exception of the adjustable seat retainer on the Mk 25. The Mk 25 has then continued to evolve, so in both the Mk 20 and Mk 25 you'll find a number of minor changes. The only one that really matters fro warm water diving is which of three possible pistons is used in the Mk 20.

The early Mk 20 piston used a stainless steel piston with a knife edge sealing surface. The mid production Mk 20 used a brass tipped stainless steel piston with a rounded seating edge, and the late production Mk 20 used a composite piston with a stainless steel piston stem with a sort of knife edge seating surface and an aceytal head. This last piston is the same basic design that is used in the Mk 25.

The brass tipped pistons display 5 psi or so of creep before they lock up, and over time some of them get damaged or worn and fail to lock up. It's a US $42 part to replace, although the odds are good that it's long since been replaced with a composite piston as Scubapro was doing that for free for a number of years when Mk 20s came in for service.

In very cold water, the very early Mk 20 could use the SPEC boot off the Mk 15 and thus seal the ambient chamber with environmental silicone grease, or if the customer didn't mind the expense Christolube or Tribolube, after the use of silicone fell by the wayside as nitrox use became the norm. With the SPEC boot and a properly packed ambient chamber, the Mk 20 w as nearly bullet proof even in very cold water - much more so than even the latest Mk 25 EVO. Without the SPEC boot, the cold water reliability comes down to how much the various internal parts have been upgraded with various TIS improvements, and what swivel cap is installed on it. The Mk 20 uses the same annual service kit as the Mk 25 and soft parts for the TIS system upgrades come in that kit, so older Mk 20s and Mk 25s get upgraded as a mater of course. You can add a later finned swivel cap and "borg" turret to a Mk 20 and that does improve the cold water performance slightly by improving heat transfer. The major thing though is to just keep the hose protectors off the metal fittings at the first stage as that will increase the available area to a much greater degree and do it for free.

In comparison the Mk 2 has a very open ambient chamber and a low enough flow rate that it transfers heat quite well and it's cold water performance is superb . Before the sealed Mk 17 came along we sold boat loads of them to both ice divers and public safety divers who needed cold water reliability. Provided the first stage is submerged before you start breathing off it, and avoid any violent free flows, the Mk 2 is a solid performer, even on an ice dive.

However, beyond the minor issue of the brass tipped piston and the cold water differences, there are no reliability issues with a Mk 20 and it is an excellent first stage capable of far better performance than the Mk 2 and it will produce better work of breathing numbers on both the S5550 and R380 second stages as the intermediate pressure remains constant. The service costs will be basically the same as the labor cost will be the same for servicing a Mk 20, and the difference in cost of the parts kits for the Mk 2 and Mk 20 are minimal.

In short, for the same money you got a much better deal with the Mk 20.

 

[chrisch]

....
the regs have arrived and looking at the service paperwork ( handwriting not great) I now believe the first stage to be a mk20. Not a mk2...

Mk20 can be upgraded at service to Mk25, so it is a good reg. (and a better bargain). Looks like a good setup to me. The service will be a bit more expensive, plus the upgrade (unless already done). I wouldn't be upset at that for 35 quid.

 

[gilbertpaul]

Mk20 can be upgraded at service to Mk25, so it is a good reg. (and a better bargain). Looks like a good setup to me. The service will be a bit more expensive, plus the upgrade (unless already done). I wouldn't be upset at that for 35 quid.

Hi all

as ever thanks for the informative and speedy responses. However on doing further research I am now even more confused

The first stage does have a plastic 'basket' around the LP ports which would seem its a Mk2 ?

The side body does have TIS pat pend, on the side ( which I thought relates to the later regs and hence Mk20)

I tried to find a look up table so I can tell for sure from the serial number]

The service report seems to state Mk20 and I checked with the seller who reckons Mk20

But why has it got a basket around the LP ports ?

To be honest I now confused and will head to the LDS

Unless there any other way to tell for sure ?

On searching there are far more Mk20 / S550 / 380 sets , than Mk2 / 550 / 380 .

sorry for being so dumb !

any thoughts very gratefully received !

Perhaps buying life support systems , new from dealers is the answer !

many thanks

Paul

 

[halocline]

You can post a picture of it if you'd like, but there are two easy ways to visually identify it as either MK2 or MK20. One, if there is a swivel on the LP ports, meaning you can rotate the LP hose connections, it's a MK20. Two, if the yoke or DIN connection forms an "L" shape with the rest of the regulator body, it's a MK20. The MK2 tank connection is in line with the regulator body.

It would be more common to see the MK20 paired with a balanced 2nd stage like the S550.

Don't fall into the trap of "life support....buy from dealers". Scuba regulators are sporting equipment, not life support.

 

[DA Aquamaster]

The plastic basket around the LP ports was a normal trim piece on the Mk 20.

If it is a straight line design with the inlet fitting on one end, a smooth cap, no LP port in it on the other end, 4 LP ports plus a HP port in between, with no swivel turret, it's a Mk 2. If it has the came basic layout but only 3 LP ports and a HP port, then it's either a late style Mk 3 or a Mk 200 (they vary a little in terms of the piston diameter).

If it is "L" shaped with the inlet fitting at right angles to the main body of the regulator, with 2 HP ports on the main body, and a 5 LP ports on a swivel turret on the other end, then it's either a Mk 15 or a Mk 20.

The Mk 15 will have a satin chrome finish that is more titanium in color, while the Mk 20 will have a normal satin or bead blasted chrome finish. Both of them had plastic trim boots on the swivel turret.

-------

The early Mk 20's have small round holes in the swivel cap (the part between the main body and the turret). Later Mk 20s have larger round holes in the swivel cap, and the last of the Mk 20s have larger oval shaped holes like the Mk 25. This is an early production Mk 20 (without the plastic trim basket). Note the small holes. The SPEC boot replaces the trim ring and extends back over the small holes.The large image at the bottom is a current production MK 2:


The large image at the bottom is a current production MK 2:


---------- Post added November 27th, 2015 at 09:20 AM ----------

Don't fall into the trap of "life support....buy from dealers". Scuba regulators are sporting equipment, not life support.

Well...outside of open water diving where you can ascend immediately to the surface - for example if you are 3,000 ft back in a cave, or are looking at a 60 minute deco obligation, your regulators are indeed life support equipment.

They are however very durable items and should be judged on condition, rather than age or used status. Scubapro has an excellent reputation for both supporting discontinued models, and for making improvements backwards compatible to older models, so there is nothing wrong with purchasing a well maintained Scubapro regulator in good condition.

 

[gilbertpaul]

Damn you guys are good

At work at the mo , so will check and if not sure load a picture tonight

To be honest sort of hoping it as a Mk20 now , growing to love it all ready and all it offers in terms of benefits

will update later when I get home

a million thanks !

 

[gilbertpaul]

Hi All

back home

LP hose dosen't swivel so = Mk2

But inlet / DIN fitting dose form a L shape !

Last owner is 99% positive its a Mk2

pictures below

Someone tell me for sure what I've bought !



PS feel a right dumb arse !

 

[gilbertpaul]

google images would suggest a Mk20 !

or is there another MK it could be ?