"RPar" wrote in message

The other unusual thing about the engine is that it is very cold
natured. It takes a very long time for the water temp to come up. I've
even gotten to the point of covering up half the radiator with a piece
of cardboard until the temperature comes up. I'm starting to suspect
that perhaps I have a thermostat that is stuck open (perhaps due to the
prolonged time in storage). Is that reasonable or is that normal
behavior for the 912 ?

If the temperature comes up to hot quicker with the radiator part covered,
you have a stuck thermostat. For the temperature to get stabilized, where
you don't see it rising and dropping a couple of degrees as the thermostat
opens and closes, is another story. (hot soak)

The radiator should not even feel warm, until the engine temperature is
almost up to normal. Is it doing that?

The thermostat is the cheapest thing in a cooling system, also the quickest
to go bad. I would not even consider running an engine that old without
replacing it.
--
Jim in NC