doctor electrons wrote ...

If you want a quick guide to wire ampacity and temperature ratings you can pick up a copy of
"Uglys" electrical reference. You can find it at Home Depot, or online cheaper i would imagine.
The tables it contains are from the NEC or National Electric Code book. It will also have the tables for
derating wire by ambient air temperature and insulation type. I took a peek at a chunk of scrap 0awg
today and its temperature rating was 105c. However, it was hi temp cable. Heres the dirt straight from the NEC big black
2008 code book.

Table 310.17 Allowable ampacities if single-insulated conductors rated 0-2000 volts in free air, based on ambient air temperature of 30c (86f)
1/0 type uf,tw 195 amps
1/0 type rhw,thhw,thw,thwn,xhhw,zw rated 75c (167f) 230 amps
As you can see the insulation affects the ampacity at temperature. The welding cable you have probably has the marking USE on it, stands
for underground service entrance. If this is the case.....
Copper, 1/0 (1 aught or zero guage) marked USE or USE-2 with a 90c temp rating has an ampacity of 260 amps.
According to the chart you should be fine, unless your temp is higher than 90c. There is a table for that as well. For example, above 80c for
this cable you would derate by multiplying the ampacity by 0.41 .. If you know the exact temp give me the number and i can tell you exactly
what to use.
(edit) At the end there, i said derating for temps above 90c then i said, "For example, above 80c". That was not an error, it is exactly as the code book reads.

MinorityCarrier wrote ...

Be aware that what you evaporate from your heated boat will coat the vacuum chamber walls, the pump foreline and get into the pump itself.
Use of a cooled foreline sieve to protect the pump, and perhaps having quartz lamps inside the vacuum chamber to heat the chamber walls might be considered.