twenty to thirty seconds. at most a minute. if not something is wrong like in need of a new water pump or clogged tell tail hose. These big motors are high volume low pressure and should start circulating water through out the system ( including the tell tail stream ) in the stated time above. the thermostats act differently on these motors unlike the 200 efi which the tell tell stream is thermostat controlled. Only discharging through the tell tell when the thermostats open.
Check the internal hose for mud dobber blockage. Mine was plugged from them damn things making a nest in there. Had to pull the hose and use my air compressor to flush out the muck. Damn bugs are small enough to make a condo in that line.
_________________________ Soldotna, Alaska..Kenai River 2011...FISHON!