Scubapro MK15 servicing question

[redacted]

The amber o-ring was made of urethane. Scubapro used them for a while (probably due to their desirable dynamic characteristics) but has gone away from them with current service kits. I only use (aftermarket) urethane o-rings if I have an extrusion problem. Otherwise I use viton. The current Scubapro kits should have a black o-ring with a red stripe (you may have to look closely). It should be noticably harder than the other o-rings when you squeeze it. That is the HP stem o-ring.

 

[bada3003]

I appreciate your input. I'm not too concerned about the color. I mention it only because there was confusion on the MK15 schematic bushings earlier and I'm trying to avoid ambiguity to the extent possible. All o-rings (whatever their color) are of smaller diameter. The backup ring was in the kit but looked used. I didn't mention it to the seller since the one in the reg is in decent (and better) shape. The seller claims the kit is direct from scubapro but packaging looked suspect. Anyhow, as long as I get the missing piston o-ring I'll chalk it up as an outlier since the seller has been prompt in responding.

I may be off base but don't assume you don't have one just because there is not an amber one in the pack. Is there a black one of the correct size? awap and couv do a lot more with SP than I do but I know at one time SP kits were a rainbow of colors but have since gone back to basic black for the most part.

---------- Post added February 23rd, 2014 at 01:25 PM ----------

Thanks. Outside the plastic backup ring the next bigger ring contained in the kit is the swivel o-ring (part #22) which has a smaller diameter.

It would be nice if there were a comprehensive o-ring inventory (of comparable material quality) that could be used for most of the o-rings found in 1st stage regs. I suspect that manufacturers inject sufficient variability so that this is not always doable. Noting that o-ring failure was the cause of the tragic Challenger shuttle disaster, it appears we're stuck with paying $20+ for stuff that takes less than a buck to make.

The amber o-ring was made of urethane. Scubapro used them for a while (probably due to their desirable dynamic characteristics) but has gone away from them with current service kits. I only use (aftermarket) urethane o-rings if I have an extrusion problem. Otherwise I use viton. The current Scubapro kits should have a black o-ring with a red stripe (you may have to look closely). It should be noticably harder than the other o-rings when you squeeze it. That is the HP stem o-ring.

 

[redacted]

It would be nice if there were a comprehensive o-ring inventory (of comparable material quality) that could be used for most of the o-rings found in 1st stage regs. I suspect that manufacturers inject sufficient variability so that this is not always doable. Noting that o-ring failure was the cause of the tragic Challenger shuttle disaster, it appears we're stuck with paying $20+ for stuff that takes less than a buck to make.

http://www.scubaboard.com/forums/repairing-your-own-gear/322518-scubapro-o-ring-sizes.html

Browse the entire thread as there are a few errors corrected later in the thread.

 

[halocline]

The amber o-rings are, I believe, duro 80 urethane. They are slightly softer than duro 90 o-rings which SP went to later on. Also I think the urethane o-rings have a limited shelf life while the EPDM o-rings from the later kits have a much longer shelf life. Short answer; I would not use the old amber o-rings in a SP kit, or at the least I'd examine them pretty closely. Urethane does have excellent abrasion resistance and resistance to extrusion, but the MK15 has the bushings to minimize extrusion anyhow. Couv really knows quite a bit about o-rings, maybe he'll chime in.

 

[bada3003]

Thanks! Will take a look.

http://www.scubaboard.com/forums/repairing-your-own-gear/322518-scubapro-o-ring-sizes.html

Browse the entire thread as there are a few errors corrected later in the thread.

 

[bada3003]

Yea, I'm getting a bit concerned about the integrity of the parts that I received. Below is a picture of the MK15 service kit I received:



I cleaned the plastic backup ring a bit, but the other parts are as received. Both the copper retaining ring and bushing have dirt/crust on them. More importantly, the two amber o-rings (parts #4 and #8 in the MK schematic since the only other part labeled "amber" is the missing large diameter o-ring, part #17) also appear used. Given the reservations you have about using the older model o-rings, the whole rationale of replacing the two piston o-rings (and generously lubing with christolube) to determine if this would fix the leak I mentioned seems in doubt.

I'm still giving the seller the befit of the doubt and will see what the condition of the missing o-ring is when it gets here. In the meantime, will take a look at the link awap pointed to.

The amber o-rings are, I believe, duro 80 urethane. They are slightly softer than duro 90 o-rings which SP went to later on. Also I think the urethane o-rings have a limited shelf life while the EPDM o-rings from the later kits have a much longer shelf life. Short answer; I would not use the old amber o-rings in a SP kit, or at the least I'd examine them pretty closely. Urethane does have excellent abrasion resistance and resistance to extrusion, but the MK15 has the bushings to minimize extrusion anyhow. Couv really knows quite a bit about o-rings, maybe he'll chime in.

 

[halocline]

Maybe you can negotiate with the seller to keep the kit but at a reduced price; you can use the seat, bushings, and snap ring, and buy new EPDM o-rings from any number of sources. You need a duro 90 010 and a duro 70 022 for the piston. The MK15 seat is tough to find, so if you can keep this one at a reasonable price it might be worth it.

 

[bada3003]

Thanks for the info and suggestion. Also, thanks to awap for helping out with my elementary questions. I didn't realize I was being helped by two resident experts until I started reading the Scubapro O-ring Sizes thread. Downloaded a bunch of useful files but still only at page 16. Most of the discussion falls outside my present scope but I'm obviously at the right place for DIY & DIR servicing of regs. Especially since both you and awap are still alive.

Maybe you can negotiate with the seller to keep the kit but at a reduced price; you can use the seat, bushings, and snap ring, and buy new EPDM o-rings from any number of sources. You need a duro 90 010 and a duro 70 022 for the piston. The MK15 seat is tough to find, so if you can keep this one at a reasonable price it might be worth it.

 

[ams511]

Maybe you can negotiate with the seller to keep the kit but at a reduced price; you can use the seat, bushings, and snap ring, and buy new EPDM o-rings from any number of sources. You need a duro 90 010 and a duro 70 022 for the piston. The MK15 seat is tough to find, so if you can keep this one at a reasonable price it might be worth it.

I do not have any Mk-15s so I could be off base; if so, I apologize.

1) Every Scubapro factory packaged kit I have ever seen has a date on it. Shouldn't the OP's kit have a date? Looking at the contents of this kit I would estimate this kit dates from the early/mid 90s. The shelf life of urethane o-rings is only 5 years.

2) I was under the impression that the MK-15 used the same seat as the MK-20 and MK-25 (and MK-10+). The MK-25 seat is a darker color, so this is either the wrong seat or an earlier version. I remember an DA Aquamaster post that Scubapro went through numerous different materials trying to perfect the MK-10+/15/20 seat (it was already perfected by the time of the MK-25). Why use an older version seat?

3) My advice (for what its worth) is to be very leery of older kits and kits that have been / could have been opened. I saw a group of older kits that were sold on eBay a while back for what I consider a ridiculous amount of money. I am not sure the bidders understood the shelf life of o-rings.

 

[halocline]

2) I was under the impression that the MK-15 used the same seat as the MK-20 and MK-25 (and MK-10+).

No, the MK15 seat is unique to that model.