Conshelf XXI or SP MK2/R190

[jvdk01]

Hello all,

I recently purchased a Conshelf XXI first and second stage that have never been used. I originally bought it with the intention of using the conshelf second as an octo with the SP MK2 first and R190 as my primary. After handling the conshelf first stage a little, I'm wondering if the conshelf first is a better choice than the SP MK2. It just feels beefier than the MK2 (and has a nice shiny chrome job). Anyways, which is the better first, and which would be the better primary/octo combination.

Thanks
John

 

[ddown]

Conshelf is balanced MKII is not. both are ultra realible.

 

[DA Aquamaster]

As much as I like Scubapro, a Conshelf 21 first stage is a better first stage with a better flow rate than the Mk 2. It's also a balanced first stage and will breathe easier than the Mk 2 at low tank pressures.

The second stages are both unbalanced dual adjustment downstream poppet designs and both breathe about the same - basically a dead heat except for the R190's adjustable flow vane (whihc is actually better to have on an octo).

 

[jvdk01]

Thank you for the inputs. That's a good point about the flow vane being better on the octo.

 

[ItsBruce]

I sure like my 21. When I first got it I tested it by breathing a tank completely empty (in 2 feet of water). Up to the last 3 breaths, it was as easy as with 3000 pounds.

 

[jvdk01]

Hopefully I never get to the last three breaths, but good to know.

 

[rescuediver009]

The second stages are both unbalanced dual adjustment downstream poppet designs ...

Who am I to correct the almighty, but the conshelf is not a dual adjustment second stage (not like it matters if you have the right tool).

The conshelf would be your best choice. The only downside that I can see to this is that it is out of warranty and thus the parts would be a little more expensive, but there are still alot of people using these, and they like them. They were the reg of choice for many of the worlds navies, at one point or another.

 

[garyfotodiver]

Who am I to correct the almighty, but the conshelf is not a dual adjustment second stage (not like it matters if you have the right tool).

The conshelf would be your best choice. The only downside that I can see to this is that it is out of warranty and thus the parts would be a little more expensive, but there are still alot of people using these, and they like them. They were the reg of choice for many of the worlds navies, at one point or another.

Parts for the Conshelf are very readily available and I, for one, have no reason to give mine up.

I learned (from a USD-trained tech) to rebuild them without using any special tools.

 

[jvdk01]

I downloaded the Conshelf XIV service manual, and doesn't seem like much to it. Can the procedures for the XIV be used for the XXI? I'm not saying that I would service it myself, just curious.

 

[knotical]

Can the procedures for the XIV be used for the XXI?

The short answer is yes.

There are some parts differences.
Assuming you downloaded a recent Conshelf XIV maintenance manual, it should cover the XIV and most similar models. For example, go to the first-stage exploded parts drawing (on page 21 in the version I have) and look at the descriptions for parts 16 and 20. You’ll see they include the alternate part numbers for the Conshelf 21.

Another difference (not covered in my manual) is the material of the second stage box top and box bottom, which results in different disassembly. The 21’s box top screws into the box bottom. Aqualung sells a tool for this, but you should be able to disassemble it with the palm of your hand, certain spanner wrenches, or if you’re careful a pair of crossed screwdrivers.