Scubapro Mk25 stiff to rotate

[thegios]

I have had a Scubapro Mk25 for a few years, always serviced at start of season after two refresh shallow dives. I do not dive a lot, probably 15 dives per year, typically between July and September.

Last year in June when I used it for the first dive the tower was very hard to rotate, all else working fine. After three dives it didn't get better, so I went for servicing: shop told me the o-ring was sort of melted. I keep the regulators in the garage where typically there's only the motorbike, hanging on the wall and covered by a plastic bag. Shop said it was probably due to fuel fumes and suggested to keep in in plastic bag into the diving bag during winter, which I did at the end of September last year.

Today I took it out and guess what: doesn't rotate, again.

Gonna bring it back to the shop of course, but if anyone has had a similar problem or has an opinion, please share.

Just to be clear: I've had it hanging on the wall for years without a single problem, only last year this started.

Thanks

 

[Mobulai]

shop told me the o-ring was sort of melted. I keep the regulators in the garage where typically there's only the motorbike, hanging on the wall and covered by a plastic bag. Shop said it was probably due to fuel fumes and suggested to keep in in a mastic bag into the di ing bah during winter, which I did at the end of September last year.

Exactly what I thought when I read the thread title, well not exactly

My guess is something regarding the oring material, could have degraded (on it’s own, some oring materials have short shelf life), or maybe fumes (unlikely tho that it only messes up the turret)
It could also be under-lubricated

Any chance you have an IP gauge? (My theory is a far fetched one):
IIRC the oring for the turret is the same for the piston head (ok maybe I’m thinking of mk10, but the theory is still the same); they still have the same shore value (stiffness/softness)

If by a far chance the turret oring was indeed degraded, you should see similar degradation on the piston head ones, and IP recovery will „drag“ and be slow after breathing/purging
The mk25 recovery is almost instantaneous, here’s what it looks like:

HP75/SP Mk25 = @mobul.ai

See Instagram 'HP75/SP Mk25' highlights from Mobulai Research Labs | System Archi. & Eng. | Diving gear nerd (@mobul.ai)

www.instagram.com

One More guess is dome salt residue from improper soaking/rinsing


Also, do you get the old orings back after service? Might have some „evidence“ to help with the guesses

 

[BoltSnap]

Exactly what I thought when I read the thread title, well not exactly

My guess is something regarding the oring material, could have degraded (on it’s own, some oring materials have short shelf life), or maybe fumes (unlikely tho that it only messes up the turret)
It could also be under-lubricated

Any chance you have an IP gauge? (My theory is a far fetched one):
IIRC the oring for the turret is the same for the piston head (ok maybe I’m thinking of mk10, but the theory is still the same); they still have the same shore value (stiffness/softness)

If by a far chance the turret oring was indeed degraded, you should see similar degradation on the piston head ones, and IP recovery will „drag“ and be slow after breathing/purging
The mk25 recovery is almost instantaneous, here’s what it looks like:

HP75/SP Mk25 = @mobul.ai

See Instagram 'HP75/SP Mk25' highlights from Mobulai Research Labs | System Archi. & Eng. | Diving gear nerd (@mobul.ai)

www.instagram.com

One More guess is dome salt residue from improper soaking/rinsing


Also, do you get the old orings back after service? Might have some „evidence“ to help with the guesses

Please use the "chain/link" for your INTG link, not just copy & paste.

 

[Mobulai]

Please use the "chain/link" for your INTG link, not just copy & paste.

Not allowed for that specific content type (story)

 

[BoltSnap]

HP75/SP MK25

 

[Mobulai]

HP75/SP MK25

Interesting you got it to work

 

[Tanks A Lot]

Degradation of the O-ring is a possibility, although I highly doubt it. If degradation were the issue, it wouldn't be confined to the turret O-ring, you’d expect to see similar damage across all environmentally exposed O-rings. That is, unless the turret itself was dipped in some kind of chemical that attacks the elastomer, most likely something petroleum-based.

It is indeed possible that the shop used the wrong lubricant. I've seen people use Vaseline as a lubricant; being petroleum-based, it causes EPDM O-rings to harden and crack. EPDM does not "melt" when exposed to petroleum based products and to cause serious issues, you'd have to expose it to a lot of fumes or very long time periods.

The more likely culprit is a missing anti-friction washer (#32). The turret is fastened to the body with a hollow bolt, which must be cushioned with an anti-friction washer. While the shop might be able to twist and turn the turret when unpressurised, once the unit is pressurised it becomes almost impossible to twist without that washer in place.

Inspection isn’t difficult either. You’ll need a C-spanner of the correct size to remove the cap, and a 7/32" hex key to remove the hollow bolt. A torque-measuring tool is highly recommended for reassembly. This could be a traditional torque spanner or even a cheap luggage scale. Torquing the bolt without a proper torque-measuring device can, and has led to problems in the past.

While I understand that many are not comfortable working on their gear, this is a really simple fix/inspection. There is nothing around the turret except the O-ring and washer. Ask the shop for the old "molten" O-ring if it turns out it is indeed the problem. I'd like to see pictures of that.

 

[Mobulai]

The more likely culprit is a missing anti-friction washer (#32).

Forgot about that one! Makes a lot more sense

 

[thegios]

Exactly what I thought when I read the thread title, well not exactly

My guess is something regarding the oring material, could have degraded (on it’s own, some oring materials have short shelf life), or maybe fumes (unlikely tho that it only messes up the turret)
It could also be under-lubricated

Any chance you have an IP gauge? (My theory is a far fetched one):
IIRC the oring for the turret is the same for the piston head (ok maybe I’m thinking of mk10, but the theory is still the same); they still have the same shore value (stiffness/softness)

If by a far chance the turret oring was indeed degraded, you should see similar degradation on the piston head ones, and IP recovery will „drag“ and be slow after breathing/purging
The mk25 recovery is almost instantaneous, here’s what it looks like:

HP75/SP Mk25 = @mobul.ai

See Instagram 'HP75/SP Mk25' highlights from Mobulai Research Labs | System Archi. & Eng. | Diving gear nerd (@mobul.ai)

www.instagram.com

One More guess is dome salt residue from improper soaking/rinsing


Also, do you get the old orings back after service? Might have some „evidence“ to help with the guesses

Apologies for replying late but oddly I did not receive any email notification.

Also, i want to clarify (and probably should be ashamed of this) that I do not have lots of tech knowledge on how regulators work: like for my motorbike, anything wrong it goes to the shop, I've know the guy for years and I trust him (he's among the very few guys in Italy that can fix my D400 ).

I brought the regulator to the shop yesterday and I'll have an answer next week.

What is strange is that for years since I bought it (6 years ago) I have never had a problem.
On Janury 2024 tehre has been a huge fire in the apartment that is right above my garage, so when in June 2024 I found out the problem for the first time, the shop said it was either the heat generated by the fire above or the fuel fumes, but since in the past years I did not have this problem we thought it had been the heat.

The breather (D420) was working fine without any problem and when Is erviced the whole set, shop told me only the turret o-ring was melted.

Shop replaced the o-ring around August 2024, i used it for another 4 o 5 dives then in September I ckeaned everything and put in the diving bag (insteda of hanging).

The other day, after 10 months I found the turret to be stiff again.

It is very hot in Italy now, but I cannor believe this may be the reason.

Let's see what shop tells me next week...

BTW: I have two Mk25: mine and my wife's. Last year both had the turret problem, both were replaced, this year mine has the problem BUT MY WIFE'S DOESN'T, and thsi is very strange vos both have been kept in the same place

 

[Mobulai]

Apologies for replying late but oddly I did not receive any email notification.

No apologies needed
And unless you activate email notifications for replies in thread, you’ll not get any except the ones on SB itself

It’s a fun exercise to try and trace the issue anyways

BUT MY WIFE'S DOESN'T

This further indicates that it had nothing to do with the fumes, just like the other environmentally exposed orings are also unaffected
But now that the issue was happening to both then only yours is even more confusing

It is very hot in Italy now, but I cannor believe this may be the reason.

it’s 39C now (at 11am) in Dahab, all the mk20/25s there are doing fine

@Tanks A Lot ‘s theory makes the most sense, the friction washer being missing — they’re far more knowledgeable and experienced than I

It could even align with / explain why an oring might look „molten“ — just crushed and worn out from shearing

Let’s see how it develops

Btw: I was just cleaning an mk20 yesterday in preparation for service, amd this post reminds me that I didn’t place that friction washer to dry — lo and behold, I did forget it inside the cleaning solution, amd ran to fish it out (I’ve serviced like 15 of these in the last year already so I’m pretty familiar, so it’s a mistake that could happen)