trevinkorea:
Is this boot widely available from scubapro dealers.
As far as I know, SP no longer stocks SPEC boots since their big push toward the TIS kit. The last time I tried to orderd one (a couple years ago), I was advised they are no longer sold and that SP no longer recommends the use of environmental silicone and in fact recommends techs remove SPEC boots when the regs are serviced. I bought the two late production SPEC boots that I have on my primary and secondary Mk 20's from a dealer who still had them on the shelf and these are the last two new boots that I have seen.
I also looked into converting to a 7ft hose and was told by my LDS that it couldn't be done on a Mark 20 G500 with a USD (oldstyle yellow) octo on a short hose. I was told that it would cause the octo to continually freeflow if the IP was udjusted high enough to provide a usable pressure to the primary on a 7ft hose.
What? That is total BS. They must not have a 7' hose in stock. Find a new LDS.
Theoretically, there will be some resistance as the air flows through the hose due to turbulence, boundary layer effects etc, but the difference in flow rates between a 7' hose and a 24" hose would not even be measureable. So it makes no difference whether the hose is 7" or 7' long, it will have the same intermediate pressure at the end.
In fact, a 7' hose can actually help a reg with mediocre flow rates as the greater volume of the longer hose actually creates a reservoir of intermediate presure air to draw on during inhalation. The Scubapro Mk 16 for example uses an internal chamber in the first stage to store IP air to provide more reserve and improve responsiveness under high demand situations. The greater internal volume of a long hose does essentially the same thing but in a low tech way.
An older USD Octo on a short hose (or any downstream design octo for that matter) will work fine on a Mk 20/G500 as long as the octo is adjusted to operate at whatever IP your Mk 20 is running. Your Mk 20's IP will be somewhere between 120 and 145 psi - like almost every other first stage currently in production regardless of brand.) Again, find another LDS. They are either really, really, ignorant or they are lying to you.
I also read the the bottom port has 15% more flow than a side port. Should I connect my 7ft hose to the bottom port. If so, would this provide enough flow to breath easily off both hoses, avoid free flow and not have to adjust the IP or detune the octo?
The port on the end of the turret is in line with the air flowing through the piston so it is a straight shot and the flow rate is a bit higher. But this difference is relative and needs to be taken in context with everything else.
A Mk 20 or Mk 25 will flow about 300 SCFM if you hook it up to a 3000 psi tank, remove the end LP port and open the tank valve. So with a 15% reduction on one of the other 4 LP ports, you would "only" have a flow rate of about 255 SCFM. But to put that in perspective, the flow rate on a Mk 16 first stage is "only" 177 SCFM and it will deliver all the air you and your buddy will ever need.
A relatively low performing second stage can only flow about 35 SCFM while a high performance second stage can move 50 to 67 SCFM. So even with two divers fully depressing the purge buttons on two high performance second stages, you are only going to draw a maximum of 134 SCFM from the first stage. Even accounting for a decrease in flow rate at lower supply pressures and for increased viscosity effects at depth, you are still going to have way more flow rate than you need from whatever port you use on a Mk 20 or Mk 25. Real life breathing rates are a lot less so you could probably use a bunch of splitters and put a dozen divers on a single Mk 20 at 100 ft and still keep everyone well supplied.
If not could you provide me with the information required to do the 7 ft hose conversion properly.
Swapping the hose is fairly simple. You need to buy the hose, remove the old hose and replace it with the new one.
The connection at the first stage end of the hose requires an ordinary open end wrench of the proper size, or even a cresent wrench. Just remember that it loosens by turning counter clockwise (Lefty Loosey) and tightens by turning clockwise (Righty Tighty). When tightening, you only want what SP describes as "tool tight" which is just snugging the fitting up with a very slight amount of pressure on the wrench - just a little beyond hand tight. You can easily strip the threads in a brass first stage if you put to much muscle on the wrench and it is even easier to strip the threads on the aluminum UL first stages. If you are not expereinced with tools in general, I recommend choking up on the wrench with your hand right up next to the head of the wrench as this will limit the leverage you can put on the fitting with the wrench.
The connection at the regulator end of the hose is more difficult. SP uses a splined nut that requires a matching specialty tool. You can get a "Just a Wrench" from Peterbuilt Tools (
http://www.scubatools.com/Scubapro.html) for $10.50 or a multitool fro $33.00. Or you can wrap some electrical tape around the splined nut and use a pair of pliers or vice grips. The tape will reduce the damage to nut but may not protect it completely. Same lefty loosey, righty tighty routine as ith the other nut.
There is also a splined nut on the second stage that secures the inlet fitting in the case and you want to be careful not to mess with that one. The hose nut jams against it so you want to be sure to only move the outside nut attached to the hose.
The long hose will have a normal hex nut fitting so an open end wrench or or cresent wrench will allow you to tighten it up. You again do not need to get it real tight, just a little bit past hand tight.
