Well.....as it turns out there was a leak in the boiler.
Ran like a champ on air but the water then dribbled out
from the boiler bottom - which has 5 heater tubes soldered
into it. Way too complex for a small boiler - and too red.
As it turns out I have another similar one from the same
source. Same complex of tubes in the bottom. I put water
in it and nothing dribbled out. I'm switching the engine
to the new boiler - already have it temporarily fitted and
it ran well on air.
So, I need to drill some new mounting holes, assemble it,
solder the steampipe, water it (try it on air again), and
then try steaming it up.
Love cobbling things together,
Wayne