Have bought this Marshall Excelsior automatic changeover. Works perfect. One problem - mounting holes at the back have no thread. I am past return window, a piece of wire and duct tape holds it so far. It "looks" like made for #8 screws. Old worn-out #8 falls right in, new #8 won't go at all - so this must be it. So... buy #8-32 tap and just do it?Btw, what is the difference of this Marshall from slightly higher priced Marshall Excela-Flo 253P and 253LP? https://www.walmart.com/search/?query=changeover%20regulator%20megr%20253Also... See that black plastic cap - it says "do not remove". The cap is sitting there pretty loose, I'm thinking to put a drop of some goo under, before I lose it.

Look on the back of the regulator. It should have 6 or so screw holes pre-drilled. Go to local hardware store and get self-tapping screws(I think they are #8x24s). Not sheet meatal screws!

They are pre-drilled, yes. Not threaded. Self-tapping screws will probably cut so-so threads, not as good a tap.So, 8-24? not 8-32?

Difference between two regulators you listed from what I've been told...253p...Packed in bubble plastic253B...Comes in box

8-32 is readily available.8-24 I don't think I have seen them , and I used to buy 8-32 and 10-32 by a box of 100 on a regular basis. A tap isn't that expensive and is easy to do if you can get to the back of the regulator to install the screws.

Changeover regulator - no thread to mount | Good Sam Community

Garry_Gayle
Explorer
Nov 29, 2018
I use the bracket and screws from the old one, they are self tapping and they are good for more than one use
NRALIFR
Explorer
Nov 29, 2018
I just replaced my regulator of the same type and it came with self tapping screws for mounting. Those holes are intentionally not threaded. The regulator body is pot metal, and will thread very easily if the correct screws are used.

:):)
enblethen
Nomad
Nov 29, 2018
Plug tap is half way between standard and bottoming.
Old-Biscuit
Explorer III
Nov 29, 2018
253 & 253P....same reg/different packaging. Both 225,000btu/hr flow rated

253L & 253LP...same reg/different packaging. Both 175,000 btu/hr flow rated
Almot
Explorer III
Nov 29, 2018
Thanks, people. Bottoming tap is also called a plug tap, right?

Yeas, must've been box vs bubble wrap... They all look the same.
enblethen
Nomad
Nov 29, 2018
Would have to use a bottoming tap. A standard tap will not cut the thread very deep into the holes. Does not really matter too much on thread count. I would use stainless screws and anti seize.
time2roll
Nomad
Nov 29, 2018
Yes just put a tap in it. 8-32, 24, 16 whatever just match the screw.
Yeti_plus
Explorer
Nov 29, 2018
8-32 is readily available.8-24 I don't think I have seen them , and I used to buy 8-32 and 10-32 by a box of 100 on a regular basis.
A tap isn't that expensive and is easy to do if you can get to the back of the regulator to install the screws.
bob213
Explorer
Nov 29, 2018
double post....
bob213
Explorer
Nov 29, 2018
Difference between two regulators you listed from what I've been told...
253p...Packed in bubble plastic
253B...Comes in box