Rusty,
I can see your point.  My ideas were motivated by my ambivalence around running both pumps all the time (I'm uncomfortable with that for reasons that I can't support really well) and the backup switch that turns on the standby pump in the event of main pump failure (that's an unknown quantity to me as far as reliability goes).  I was looking to examine as many failure modes as possible.  Of course, as just occurred to me, the backup pump switch would be exactly as reliable as the overtemp alarm, since they'd both be driven by identical (if not the same) detection device.

You're right in saying that we both have to make our own estimates of the unknown consequences of various failures, and you're the man in the driver's seat here.  Keep up the good work.  Your research is going to relieve me of that chore.  Don't think I don't appreciate that.

Keep them cards and letters comin' .... Jim S.

Russell Duffy wrote:

If it was me, I'd do a little testing - start at cruise at altitude - and shut off the pump and see what happens and how fast.

I'll just have to wait and see how it works for you, because there's no way I'm doing it.  I think you're closer to underestimating the damage, than I am to overestimating it, and if I have to be wrong, I'd much rather be on the safe side.

  I think the temps will rise slowly enough to give you plenty of time to turn on the backup in case of failure of the primary.I'm sure the temp "gauge" will rise slowly, because there's no water flow, and the sensor isn't near the combustion chamber.  I'm also sure that the combustion area of the block will be overheating like crazy.  Why would you intentionally subject your engine to that? Rusty

--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T