will BP series II manual mill run on 208 3p?

According to : I think that the important thing is to check the labels on the motor. Many of them can be rewired for either 480 or 240 -- and 240 *might* run reasonably on 208.
Aside from that -- what other things consume electrical power on a manual Series II? My CNC Series-I can be rewired for 240 or 480, with lots of jumper straps inside electrical cabinets, plus the motor itself being rewired for the voltage at hand using what was designed into the motor.
Well ... *if* that spindle motor can be rewired for 240, it *Might* be happy on 208. The rest of the machine (power feeds, lube pump, lights, etc, can probably be fed through a *much* smaller transformer, which is probably already somewhere in the machine. Some things, like the oil pump and the lights are probably already 120V devices, and simply need switching taps on a transformer in the machine to be happy.
If the spindle motor is not happy with 208, you will need some form of step-up transformer. I think that your 208 is delta wired, and the 240 would be Wye wired.
Note that I have read here of Bridgeport motors wound for an even higher voltage -- for somewhere in Canada, IIRC, and switching to a different voltage involves either a transformer or a rewinding (or replacing) of the motor.
Good Luck, DoN.

208V is standard for 3ph Y connections i.e. 120/208V Y. 240V would be delta configuration.
Buck-boost type transformers could be used to boost 208V to something like 232V if the motor isn't happy at 208V. Buck boost transformers are pretty common and cheap used.
Yet another option is a VFD to run the motor from single phase power where a single buck-boost transformer would work and you'd get the soft start and variable speed benefits of the VFD.
Pete C.

snip--
I think you have it backwards, DoN. I have three phase delta service, and it's 240 volts. Everything I've read indicates that 208 is Wye.
Harold

The motor windings can be either wye or delta can be rated for any voltage at the whim of the manufacturer. The utility service entrance configuration (almost always a grounded wye)has no relationship to the motor winding connection.
Randy