Article 121858 of comp.os.vms:
Hein RMS van den Heuvel (vandenheuvel@eps.enet.dec.com) wrote:

:     Using $PATCH/ABSOLUTIVELY/NONEW <workdir>MAILSHR.EXE that would
:     look something like:

: 	PATCH  Version 5-05    20-June-1991
: 	IMAGE FILE BEING PATCHED:	"USER9$:[VANDENHEUVEL]MAILSHR.EXE;1"
: 	DATE/TIME OF PATCH:		 4-APR-1997 23:07:06.05
: 	PATCH>def x = 2e * 200		! VBN number minus 1
: 	symbol "X" defined as 00005C00
: 	PATCH>ex/inst x+8		! Offset of instruction in VBN
: 	00005C08:  MOVW    #5003,(R6)
: 	PATCH>ex/inst
: 	00005C0D:  MOVW    #0F1F,B^16(R6)
: 	PATCH>repl/inst .
: 	OLD>  'movw #0f1f,b^16(r6)'
: 	OLD>  exit
: 	NEW>  'movw #0202,b^16(r6)'	! I tried FAC=GET, SHR=GET
: 	NEW>  exit

Well, of course my movw instruction was in VBL 42 and not 47 as in your
example.  I'm still running VMS V6.2, so perhaps you patched a 7.1 image?
Anyhow, this works like a charm.  Thanks for the tip! 

Jonathan Boswell