Scubapro MK 7 Rebuild Question

[73diver]

Scubapro and authorized dealers will no longer rebuild the MK7. The Scubapro folks will replace a MK7 with a MK25, for the cost of a repair. I have already taken advantage of that lifetime warranty for my 1973 MK7.

I bought my wife a 3000PSI MK7 in 1981 which she used until 1984. Then kids, graduate school, etc. Where did the time go? Now I'm retired and diving like a person possessed. I have decided to rebuild that regulator and use it for relatively shallow recreational diving.

I have obtained a rebuild kit including the Teflon first-stage piston seat and the 'flat' filter. I have disassembled it nearly completely and performed a couple hours of cleaning. It looks brand new inside and out.

My question as follows: There is an o-ring (labeled #25 in the schematic) that provides a seal between the first-stage body and the piston shaft. The o-ring fits into a groove machined into the body. The only portion of the o-ring that is visible is the inside edge where the piston shaft passes through it. I can see that there is a 'ragged' edge so for sure I need to replace it. Are there any tips for getting one of these deep o-rings removed and replaced without 'hacking up' the adjacent smooth surfaces?

Thanks,

Ken

 

[redacted]

That is a critical o-ring and needs to be replaced with a 2-010, duro 90 to get a reliable seal.

The critical sealing surface is the LP side of that gland so that is what ytou need to avoid scratching. favorite tool for removing that o-ring is a double hood pick (O'ring Pick, Double Hook, Plastic Handle). I work is down one side of the o-ring and twist the handle to hook the ring and lift it out. Alternatively you can use a straight pick and stab the o-ring. But you must work from the LP side of the gland to avoid scratching the critical sealing surface.

Installing the new o-ring may take a couple minutes if you get lucky or a couple days if you have to order one of Herman's special tools (http://www.scubaboard.com/forums/do...tools-mk-5-mk-10-piston-stem-o-ring-tool.html). I usually lube the o-ring well, twist it into a figure "8" to get it started, and then work it into the gland. I use a wooden dowel and picks but again you must be very careful not to scratch the sealing surface. Toothpicks would probably be safer than metal (SS) picks.

Good luck. BTW, I don't know why you would limit a Mk7 to shallow dives. Mine go anywhere I would go. Enjoy

 

[PfcAJ]

Whoa there. SP will replace a mk7 with a mk25? Do you need paperwork to prove you're the original owner or something?

 

[73diver]

I wanted to have my Mk 7 serviced. My LDS does not repair Scubapro of any kind. So, I looked for an authorized Scubapro service provider near me. I took it there, he looked at it and said he was not allowed to work on Mk 7's, but if I was the original owner it would be replaced with a Mk25 for the cost of biannual service ($75). I had to retrieve the little credit card (warranty card) that identified me as the original owner.

 

[PfcAJ]

ahh, gotcha.

 

[73diver]

That is a critical o-ring and needs to be replaced with a 2-010, duro 90 to get a reliable seal.

Good luck. BTW, I don't know why you would limit a Mk7 to shallow dives. Mine go anywhere I would go. Enjoy

Thanks AWAP. The schematic describes that particular o-ring as 'amber.' That must have been the way to assure duro 90 at the time. Your advice on removal and replacement in confined space is very much appreciated. Ken

 

[LeadTurn_SD]

One more "plug" for the Double Hook pick awap recommended. I have that pick, and it has become my "go-to" o-ring remover whenever I encounter a tough-to-reach o-ring, or even just a plain stubborn one. Really worth its weight in gold.

Best wishes.

 

[redacted]

Thanks AWAP. The schematic describes that particular o-ring as 'amber.' That must have been the way to assure duro 90 at the time. Your advice on removal and replacement in confined space is very much appreciated. Ken

That is an older schematic (of course - it is a mk7) from when Scubapro was using urethane o-rings in that and a few other applications. I believe modern kit have a black o-ring with a red stripe (to differentiate it from other black 2-010 o-rings in the kit) that is their recommended hardness. I still usually use urethane in that application. They are a bit more expensive than the more common vitron but also have better dynamic qualities desirable in that application.

I am somewhat surprised your local scubapro dealer would not do the service. The HP seat are the same as are used in the still supported Mk10. The rest is standard o-rings and that standard sized flat filter. I tend to be a bit foot heavy so I often use a Mk7. They tend to be a good conversation piece.

 

[JohnN]

Scubapro and authorized dealers will no longer rebuild the MK7. The Scubapro folks will replace a MK7 with a MK25, for the cost of a repair. I have already taken advantage of that lifetime warranty for my 1973 MK7.

I bought my wife a 3000PSI MK7 in 1981 which she used until 1984. Then kids, graduate school, etc. Where did the time go? Now I'm retired and diving like a person possessed. I have decided to rebuild that regulator and use it for relatively shallow recreational diving.

I have obtained a rebuild kit including the Teflon first-stage piston seat and the 'flat' filter. I have disassembled it nearly completely and performed a couple hours of cleaning. It looks brand new inside and out.

My question as follows: There is an o-ring (labeled #25 in the schematic) that provides a seal between the first-stage body and the piston shaft. The o-ring fits into a groove machined into the body. The only portion of the o-ring that is visible is the inside edge where the piston shaft passes through it. I can see that there is a 'ragged' edge so for sure I need to replace it. Are there any tips for getting one of these deep o-rings removed and replaced without 'hacking up' the adjacent smooth surfaces?

Thanks,

Ken

I would hardly categorize myself as a SP rebuild expert, but I believe the MK-7 shares the same construction as the MK-5 (which I successfully rebuilt).

I found the following link very helpful: http://www.scubaboard.com/forums/do-yourself-diy/422293-diy-balanced-piston-stem-o-ring-tool.html

 

[Couv]

The cork and dowel work well, but for the price of a cheap bottle of wine you can get one of Herman's purpose built tools and eliminate the possibility of cork particles fouling the moving parts. See my review here: http://www.scubaboard.com/forums/do...tools-mk-5-mk-10-piston-stem-o-ring-tool.html and purchase one here: Shop Online

Now I just need to talk Herman into making an o-ring removal tool for that bastard o-ring.