Scubapro Mk 10 help?

[APKS]

Hi,

I recently brought my Mk 10 for a service. and was surprised when the tech said that the standard HP seat from Scubapro did not fit it and the IP crept up very slowly.

he said he thought it was an earlier model and offered to replace the high pressure chamber end - piston, piston base and HP seat to make it a Mk 10. He said The turret and middle parts were identical to the standard Mk 10 circa 1990.

The reg is not a Mk 5, Mk 9 or Mk 10 plus or any later version. It looks identical to the mid 80's Mk 10s but not the 1990 Mk 10 (the one with the black plastic around the middle).It lacks the plastic and the HP chamber end is slightly slimmer.


Is there some difference between the 1980s Mk 10s and the 1990 model?
Is it possible to "upgrade" it

Any opinions please

Ash

 

[DA Aquamaster]

I am not sure what you mean when you say "the HP chamber end is slightly slimmer". This raises the possibility that your reg, or at least this part of it, is one of the many Mk 10 clones that were made after the patents expired. Tusa for example marketed an exact mechanical copy of the MK 10 that shared the same parts and even had cross referenced part numbers (Tabato made the MK 10 for SP and Tusa is just "Tabata USA").

The only difference ever introduced on the Scubapro Mk 10 body was the groove for the spec boot that appeared on later models. The HP seat also sits in the seat retainer, so I would not see the point in replacing the whole main body unless it were not an original SP part. Damage or wear in the area where the HP O-ring seats causing a leak or HP O-ring pinch is normally the only reason for replacing the main body and both would be cause for warranty replacement as wear is a covered issue and damage would only be caused by a tech getting careless with an O-ring pick.

Normally, when you have a problem getting the IP to lock up with a Mk 10, the first thing to try and replace is the seat (sometimes even a new one can be bad). Next you would normally consider replacing the piston as the sealing edge can become damaged or worn. If however the reg came into the shop with a flat seat and you are replacing it with a new conical seat, I would consider swapping seat retainers to see if this makes a difference.

In some cases a seat retainer will not be perfectly concentric and will hold the seat slightly off center. This was not an issue with the old flat seats where being a bit off center did not prevent an effective seal as long as the seat retainer/seat were not rotated between service intervals. With the new conical seats, a higher degree of precision is required to keep the hard sealing edge of the piston stem properly centered to effect a good seal and an off center seat retainer can cause problems with getting a good IP lockup.

One problem I have encountered with older Mk 10's is that main springs can get a bit stiffer over time (decades) and the IP consequently increases. But SP now offers 3 separate seats of slightly greater heights in the annual service kit and one of the two additional seats will normally bring the IP back within range. (If not, spring replacement resolves the problem.) Consequently, it is important to determine that the IP is really creeping, rather than just being excessively high.

But my best recommendation for a fix is to have the tech try a different seat retainer known to be concentric and if that does not do it, then to replace the piston. You probably need one part or the other replaced and in very rare cases maybe both. Dealer cost should be around $20.00 US for the piston and $5-7 US for the seat retainer.