New life for an old MK3

[Eric Sedletzky]

I cross posted this from the DIY forum.

A friend of mine gave me this old Scubapro MK3/108 reg.
It's probably from the mid to late 60's, thin yolk, 2 LP ports & one HP port.
The thing has quite a history. First of all it was never serviced once in it's entire lifetime.
The guy who gave it to me was primarily a freedive spearo. He only used the reg occasionally to go deep in Florida to shoot groupers and also to dive in Southern California for scallops and occasionally lobsters. He actually could care less about scuba or the gear.
He only used it with one single second stage, no octo or SPG. When it got hard to breath he came up. It was about as simple as that.
He actually bent himself while using this reg. He was diving in Florida and went to 200 feet on a single AL 80, no SPG, on air. He was doing his stops according to navy tables and ran out of air somewhere in the 50 foot range and had to do a free ascent and as such blew off a bunch of deco, (yeah I know, genius!). The result was within a few minutes his shoulder blew up with gas under the skin (subcutaneous embolism) and looked like somebody filled his skin with air. After that his shoulder hurt like hell in the joint and since then he's had 5 surgeries to try and fix the damage. He never did go to a chamber. That was probably 20 years ago
I'm not sticking up for the guy and I certainly don't approve of his cowboy diving but those are the facts.
The point is, that simple little MK3 went to 200 feet and worked fine.

When I got it it was nasty, corroded, frozen up, it had never even been rinsed one time after he used it in salt water!
I very carefully took it apart and the chrome was so bad and pitted that I decided to just strip it off and try polish out the brass. So far I have the 1st stage done and I've almost got the yolk done.
Next I'm going to work on the diaphram cover and the clamp rings. I don't know what I'm going to do with the 2nd stage body yet, if I'm going to just clean it up or strip off the chrome and polish it.
After all that I'm going to soak it and rebuild it. It's about the dirt simplest reg internally I've ever seen.
I don't have an ultrasonic cleaner. I was thinking of getting one of those $79 ones at Harbor Freight but I'm wondering if CLR would work. It's supposed to disolve salts, scale, rust, corrosion, etc.
Can anybody advise on CLR to soak reg parts?

Here are a few photos of my progress so far:
The pics of the second stage are obviously before shots. Stay tuned, when I am done they will be beautiful!
The first stage used to look like the 2nd stage parts you see.

 

[SwimJim]

You can use a solution of vinegar and water mixed 50/50. For minor stuff I usually let it sit about 15 minutes. This one is going to take more time. This solution is hard on the chrome so only soak as long as needed. A better product that can be ordered over the net is SaltX. That does a nice job and is easier on the parts. I'd say the chrome on that 2nd stage is shot anyway. You'll probably have to get it rechromed to make it look like anything.

 

[Eric Sedletzky]

You can use a solution of vinegar and water mixed 50/50. For minor stuff I usually let it sit about 15 minutes. This one is going to take more time. This solution is hard on the chrome so only soak as long as needed. A better product that can be ordered over the net is SaltX. That does a nice job and is easier on the parts. I'd say the chrome on that 2nd stage is shot anyway. You'll probably have to get it rechromed to make it look like anything.

No, I want the chrome gone. I'm going to strip it off anyway and polish up the brass like I did on the 1st stage.
Thanks for the tip.

E

 

[DaleC]

looking forward to the finished result...

 

[Rich Keller]

ZKY, That is the set up I use as a travel regulator! It is light, dependable and easy to field strip and repair if needed. The MK3 I have though is rated for 3000psi and the 108 in an HP. Your 108 looks different then the ones I have seen before, the port for the air inlet looks like it is from a 108 but the exhaust port is a 108HP. You might have something rare there but I am not an expert on the subject.

 

[Eric Sedletzky]

ZKY, That is the set up I use as a travel regulator! It is light, dependable and easy to field strip and repair if needed. The MK3 I have though is rated for 3000psi and the 108 in an HP. Your 108 looks different then the ones I have seen before, the port for the air inlet looks like it is from a 108 but the exhaust port is a 108HP. You might have something rare there but I am not an expert on the subject.

The guy I got it from used it with 3000 psi all the time on an AL80.
I know you're not supposed to use that pressure with a thin yolk but he seemed to get away with it. I may look into getting a thicker yolk for it.
I still can't get over how simple the reg is inside, wow! And to think the dive shop wanted $40 for a rebuild kit and $65 to put it in.
I replaced a few O rings and got a new rubber purge button for it and I'm in it $14 total and about 30 minutes in rebuilt time. The polishing is another story but that was fun.

Here is a photo of the finished second stage:

 

[Rich Keller]

The guy I got it from used it with 3000 psi all the time on an AL80.
I know you're not supposed to use that pressure with a thin yolk but he seemed to get away with it. I may look into getting a thicker yolk for it.
I still can't get over how simple the reg is inside, wow! And to think the dive shop wanted $40 for a rebuild kit and $65 to put it in.
I replaced a few O rings and got a new rubber purge button for it and I'm in it $14 total and about 30 minutes in rebuilt time. The polishing is another story but that was fun.

Here is a photo of the finished second stage:

I used an even older Healthways first stage on a 3000psi tank for years and never had a problem. The most anyone at a dive shop will say about it is that they were not rated for 3000psi but not that they can not be used though all want to replace it.

 

[Ed Palma]

ZKY, how'd you get the chrome off? Mechanical or chemical? I've got an USD reg that I was thinking of rechroming, though this looks kinda fun too.

 

[Eric Sedletzky]

ZKY, how'd you get the chrome off? Mechanical or chemical? I've got an USD reg that I was thinking of rechroming, though this looks kinda fun too.

I just took 240 grit 3M gold automotive grade sandpaper on a small orbital sander and carefully sanded it off. In some places where I couldn't get the sander to get into I hand sanded it off.
Then I took some green rouge on a cotton buffing wheel on a bench grinder and polished it up. You could probably go over it with 400 grit but brass is so soft that 240 scratches buffed right up. Brown tripoli rouge would work too although it's a little courser.

The other buffing wheel that could be used would be a small disc cotton buff in a mandrel like the ones they sell in a kit at Harbor Freight. Those would work too, but an electric drill is too slow, you need about 3000 rpm or higher so maybe a dremel tool?
I have air power so I would use a die grinder instead of a drill.

The final polish you do by hand with something like Brasso. I have other metal polishing cremes but brasso would be fine. Brasso would also be used to periodically brighten it up.

 

[Tony Atomic]

I just got two sets of SP regs: a 109/MK1 and a 108/MK3. They both are in decent shape, but the 108 is a little rough and I think a lot of the chrome will be coming off when I clean it up. There is some pretty bad pitting going on. Is the brass going to be eaten by saltwater or will it be okay if I thoroughly rinse it after every dive?