1997 Honda BF75A Overheat warning

[Hal in PSG]

Engine ran fine for a couple of hours and then I got the intermittent beep and the RPM dropped.
The flow indicator was working fine.
The engine was not particularly hot to the touch.

I replaced the thermostat (I believe there is only one on this carbureted model) but still getting the alarm.

Any help would be GREATLY appreciated.

Thanks, Hal