Thought I would post the fix to my overheating
problem. All things pointed to a faulty fresh-water pump (recall that the raw water
side was good, no apparent blockages in the fresh water
system). So before I called in the cavalry I thought I would pull the fresh-water pump. I knew within a couple of minutes that that was the problem as once the alternator
belt was off, the pump pulley spun with zero friction. It just free-wheeled!
Pulled the pump and the shaft had sheared just inside impeller housing. There was no indication of pump failure wrt to leaking coolant
. Only symptom was no fresh water
flow. I ordered a new pump from the local Perkins
supplier, pulled the old pulley, pressed it on the new pump. Once installed and the system bled (including the plugs on the top of the cylinder block) all was good!
In retrospect, I could/should have figured this out very quickly. As is always the case, when there's a sudden and catastrophic overheating
issue it's most likely a component failure. First thing to check is a blown hose, closed sea-cock,etc. The second is the raw water
circuit. Once that is eliminated, it's likely not a blockage in the fresh-water system as these system is closed and most likely any blockage would be partial in nature and build up over time. This leaves the thermostat and raw-water pump. I could have easily pulled the alternator
belt before removing the thermostat and tried to spin the pulley. That would have told me right away what the problem was.
Having said all that, I did learn a ton. Especially from all the other problems that others had solved
in different ways.
Thanks everyone for helping out! Much appreciated