Thanks for the input. Another frustrating test today:
Ran it at the dock in idle for 15 minutes - good telltale, cold/cool stream, thermal reading of 126.8 deg F
Bumped up idle for 5 min - increased telltale, cold/cool, 129.8 deg F
Bumped up for 5 min - increased telltale, cold/cool, 131.6...