A constant beep and then she goes into limp home mode?
That sounds like an oil warning, if so.
Is this happening on the water or while you are flushing ashore?
OK
You will get a consant alarm if water flow is interupted
Weed/ poly bag etc as you know
That could be one 'diagnosis'
Especially if She fired up ok later
Water peeing out ok?
Less likely to be an oil based prob with a 4 stroke
The 2's will shout if oil is low
Easy enough to 'dip' the oil though isn't it
Just fixed a slighlty smaller one
Was the thermostat
Take cover off
Take plastic cover off and there is the thermo housing
Go down that route first tiss quite easy.