Two MK25s That Look Different? Help.

[realdiver7]

Can someone tell me the differences between the Scubapro MK25 1st stages? I have seen MK25s with the usual round looking design, and I have seen MK25s with a "layered" look on the outside, with several round edges that encircle the entire 1st stage.

Is one style the AF (anti-freeze), or are all MK25s classified as AF with a teflon coated piston, etc.? Which style is better, newer, more advanced, etc.?

Thanks.

 

[DA Aquamaster]

The early production Mk 25 had what was basically a Mk 20 swivel cap with larger oval shaped holes into the ambient chamber.

The present Mk 25 has the "borg" turret with the heat transfer fins. The fins are designed to improve heat tranfer and make the reg a bit more freeze resistant but the full AF kit came out a few months after the fins.

The full AF kit consists of a composite piston with a mirror polished stem, a plastic cover that insulates the piston head, a little flexible rubber boot on the piston stem, a teflon coated main spring, and the finned swivel cap. Any Mk 25 prodiced after June 2003 should have the full AF kit. Since all current Mk 25's have the AF kit, (and all the older ones can be upgraded) Scubapro does not call anything a "MK 25 AF" but AF kitted Mk 25's are often referred to by divers as Mk 25 AF's to distinguish them from earlier non-upgraded Mk 25's.

You could add the finned swivel cap for about $20.00 at your next annual service. But personally, I don't think the fins make much difference in cold water performance. I used a Mk 25 D400 without the fins for about a 100 or so dives in water temps in the mid 30's to mid 40's with no freeflow issues. I'd make sure the rest of the AF kit is in there at your next annual service, but I would not worry much about the fins unless you want your regs to match.

 

[realdiver7]

Thank you very much! That helps out a lot.