In article s.com, "Karl Townsend" wrote:
I have an underground wire that I think is called #8-3 but I can't find any
numbers on it.

Keep looking. It's there -- you just haven't found it yet.

The OD of the insulation is 0.238" on each of the three
wires.

Not relevant.

That in turn is in another insulated jacket for underground. Each
wire is a seven stranded unit, the O.D. of this is 0.145" and each wire
measures 0.048". What's the wire size here?

Dunno. The standard for AWG8 is 0.128", AWG7 is 0.144" -- and AWG7 would be
unusual, to say the least, for electrical wire.

More importantly, I need to know amp capacity. There's four of these #8?-3
wires in a conduit for four feet going from the main to underground.
(Multiconductor may reduce amp rating?)

I want to go 40 amp circuit breaker. Am I OK

Not possible to answer, without knowing exactly what kind of cable you have.
It's marked somewhere on the cable sheath. Keep looking.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.