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I have received nothing as yet. I'll check again tomorrow, although it's usually instant, strange.
How to restore a Scubapro Mark VII Honker
- Thread starter rsingler
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I have received nothing as yet. I'll check again tomorrow, although it's usually instant, strange.
thbcthomas
Contributor
OP
Perfect for taking pictures head down underneath a ledge! 
Or to counterbalance Jet Fins!
Or to counterbalance Jet Fins!
thbcthomas
Contributor
Oh hell, they are fun to rebuild and what else you got that`s gonna honk at you underwater?
cool as hell thx for the detailed blow by blow ..ive never had one on the bench ....
Wow very informative and complete.I did the repair course twice starting in 1977 from Pete Wolfinger!
OP
I have (belatedly) been edjumacated by @Luis H on the true history of the shouldered Mk5/Mk7 piston. The piston was not recalled, and there is no weakness in the pistons without a shoulder.
Post #2 on page 1 above has been modified to include the following:
"It should be noted that the Mk5 (and presumably the Mk7) piston was replaced with a piston with a large shoulder at the base of the piston shaft. I do not have a Service Bulletin that specifies this for the either the Mk5 or Mk7. However, sometime between Mk7 Rev B in 1974 and Rev H in 1984, the piston 101-4 was replaced with the 10.101.003. However, from Mk5 schematics as late as 1981, piston 10.101.003 was not yet a shouldered piston.
Sometime between 1981 and 1984, the piston was modified to add the shoulder. However, the piston part number did not change as late as the Mk7 Revision S in 1994, or the Mk5 Revision V in 1997. EDIT: The reason for the piston replacement was the small risk of the knife edge becoming embedded in the (then) flat seat. The conical seats had not been introduced yet, and the shoulder provided a stop beyond which the piston could not travel, preventing it from burying itself in the seat. There was never a piston recall, despite rumors to the contrary."
It's nice for those of us with lots of unshouldered Mk5 pistons (and conical seats) to know they were never recalled. I apologize for my earlier error.
Interestingly, a similar move with a small spacer was performed on the old Calypso III and IV, for the same reason.
Post #2 on page 1 above has been modified to include the following:
"It should be noted that the Mk5 (and presumably the Mk7) piston was replaced with a piston with a large shoulder at the base of the piston shaft. I do not have a Service Bulletin that specifies this for the either the Mk5 or Mk7. However, sometime between Mk7 Rev B in 1974 and Rev H in 1984, the piston 101-4 was replaced with the 10.101.003. However, from Mk5 schematics as late as 1981, piston 10.101.003 was not yet a shouldered piston.
Sometime between 1981 and 1984, the piston was modified to add the shoulder. However, the piston part number did not change as late as the Mk7 Revision S in 1994, or the Mk5 Revision V in 1997. EDIT: The reason for the piston replacement was the small risk of the knife edge becoming embedded in the (then) flat seat. The conical seats had not been introduced yet, and the shoulder provided a stop beyond which the piston could not travel, preventing it from burying itself in the seat. There was never a piston recall, despite rumors to the contrary."
It's nice for those of us with lots of unshouldered Mk5 pistons (and conical seats) to know they were never recalled. I apologize for my earlier error.
Interestingly, a similar move with a small spacer was performed on the old Calypso III and IV, for the same reason.
Thanks to Rob's excellent tutorial, today the world has another formally quiet MK VII ready to make noise.
OP
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