Scubapro Mk2 and Mk2+
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halocline
Contributor
I think the difference between the MK2 and MK2+ is with the TIS antifreeze stuff; if I remember it's basically a bushing on the piston and a coated spring. I don't think I've ever actually opened up a MK that was not a "+".
The MK10 is a great 1st stage, an ideal reg to buy used. I actually prefer the MK5 a little, but it's tougher to find a late model MK5 in excellent condition, while there seems to be many more MK10s available in excellent condition. The main difference is the MK10 uses a smaller, lighter piston and the body fits together a little differently.
One thing that I think is really important but is not often considered when buying a used one of these regs is the turret bolt. Most MK5s have a brass turret bolt which is easily damaged by over-torqueing. By the time the MK10s were out, I believe SP had mostly switched over to the stainless steel turret bolt which is stronger. This is only an issue if you buy one that has been man-handled by a zealous tech, because finding a replacement bolt is difficult.
My favorite used 1st stage would be a late model MK5 in excellent condition inside and out with 5 LP ports and a stainless turret bolt. I've bought several MK5s and only found one that fits that description. Both of the MK10s I've bought are in great shape, although one had some small scratches on the piston shaft and creeped a bit. I replaced the piston with a NOS piston and it locks up really well.
An overlooked good candidate for used regs is the MK15; personally I like it better than the MK20 and it does not have the same problems with the different generations of pistons that the MK20 has. I bought a MK20 once with the middle generation brass-tipped piston and had a terrible time keeping it from creeping. Finally after a few hours of polishing the piston edge with micromesh it worked fine, but I'm still going to replace the piston with the MK25 composite piston. That's about $50-60 if you can find a SP dealer willing to sell one. The MK15 uses the older style knife edge piston and has really stable IP. It's considered a little more challenging to work on, only because you need a long skinny set of snap ring pliers to replace the piston bushings. One you have the tool it's no more work than any of the other balanced pistons, IMO.
The MK5 and MK10 lack the bushing system found on the later SP piston regs, so you have be careful removing and replacing the HP piston o-ring. I'm sure more than one of these regs has been ruined by a careless tech scratching the seating surface of the o-ring digging it out with a pick.
The MK10 is a great 1st stage, an ideal reg to buy used. I actually prefer the MK5 a little, but it's tougher to find a late model MK5 in excellent condition, while there seems to be many more MK10s available in excellent condition. The main difference is the MK10 uses a smaller, lighter piston and the body fits together a little differently.
One thing that I think is really important but is not often considered when buying a used one of these regs is the turret bolt. Most MK5s have a brass turret bolt which is easily damaged by over-torqueing. By the time the MK10s were out, I believe SP had mostly switched over to the stainless steel turret bolt which is stronger. This is only an issue if you buy one that has been man-handled by a zealous tech, because finding a replacement bolt is difficult.
My favorite used 1st stage would be a late model MK5 in excellent condition inside and out with 5 LP ports and a stainless turret bolt. I've bought several MK5s and only found one that fits that description. Both of the MK10s I've bought are in great shape, although one had some small scratches on the piston shaft and creeped a bit. I replaced the piston with a NOS piston and it locks up really well.
An overlooked good candidate for used regs is the MK15; personally I like it better than the MK20 and it does not have the same problems with the different generations of pistons that the MK20 has. I bought a MK20 once with the middle generation brass-tipped piston and had a terrible time keeping it from creeping. Finally after a few hours of polishing the piston edge with micromesh it worked fine, but I'm still going to replace the piston with the MK25 composite piston. That's about $50-60 if you can find a SP dealer willing to sell one. The MK15 uses the older style knife edge piston and has really stable IP. It's considered a little more challenging to work on, only because you need a long skinny set of snap ring pliers to replace the piston bushings. One you have the tool it's no more work than any of the other balanced pistons, IMO.
The MK5 and MK10 lack the bushing system found on the later SP piston regs, so you have be careful removing and replacing the HP piston o-ring. I'm sure more than one of these regs has been ruined by a careless tech scratching the seating surface of the o-ring digging it out with a pick.
If you know for sure the Mk 10 is in good condition I would say $50, maybe a bit more if recently serviced. I have bought a couple of them off ebay lately mated to a good second stage (G200B and D300 with console) for under $100, both looked good on the outside, but needed a good cleaning/service on the inside. One was in surprisingly bad shape inside (corrosion, crushed o-rings, etc.) considering the mint looking exterior, IP lock up was good, but low 115 psi with no creep. If diving in cold water be aware the Mk 10 went throuugh several variation related to the SPEC anti icing system (silicone filled ambient pressure chamber) the newest variant had the black Mk 10 yoke screw knob, and a black ruber ring around the vent holes that fit into a recessed groove.
Ike
p.s. be aware the Mk 10 is designed to work with 3000 psi tanks, I have used mine with 3200/3300 psi tanks over the years with no problems, higher pressures may cause o-ring extrusion.
Ike
p.s. be aware the Mk 10 is designed to work with 3000 psi tanks, I have used mine with 3200/3300 psi tanks over the years with no problems, higher pressures may cause o-ring extrusion.
As far as I know there were only two major variations in the Mk 10 body - the later ones with holes and a groove for a spec boot and the early ones with holes and no groove for a spec boot.
There are 2 or 3 different Mk 10 pistons if you include the Mk 10+ piston and a post production piston TIS style piston that incorporated a plastic bushing near the head as well as someo fthe flow improvements of the MK 10+ piston.
The blakc knob was acommon upgrade but was an aftermarket upgrade on nearly all Mk 10's as it arrvied either at the end of Mk 10 production or during Mk 10+ production.
There are 2 or 3 different Mk 10 pistons if you include the Mk 10+ piston and a post production piston TIS style piston that incorporated a plastic bushing near the head as well as someo fthe flow improvements of the MK 10+ piston.
The blakc knob was acommon upgrade but was an aftermarket upgrade on nearly all Mk 10's as it arrvied either at the end of Mk 10 production or during Mk 10+ production.
I have examples of all 3 kinds, I will try to post photos some time, as I need to rebuild at least one of them before going on vacation in a couple of weeks.
The differences in the case are:
Smal vent hole only
Countersunk hole with small vent hole in the bottom (this variant was only on the market for 1-2 years)
Countersunk hole with groove for rubber boot
This all relates to the SPEC silicone injection, the original small hole only model had to be packed with silicone before reassembly, the counter sunk holes made it possible to inject the silicone after reassembly making servicing much less messy, the addition of the groove and rubber boot help keep the silicone in, and debris out.
Ike
p.s. the black yoke knob arrived in 1988, maybe 1989, so probably about 3-5 years before the Mk 10+
Hoosier
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I am not sure if you hit a nail on the question.
A black bushing is included in an annual service kit. I don't know if this black bushing is acted as TIS. Whenever I open MK2 (I had about 10 MK2s), 4 out of 10 MK2s don't have a black bushing inside. To be honest, I can't notice any difference in my diving environment, 41 degree water.
Just my 2 bar.
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