Honda Outboards BF40A/BF50A Service Manual, Page 219Get this manual
HONDABF35A45A 2) Operation
1When the oil pressure switch or thermo switch detects the trouble signal, the comparator circuit compares the condenser discharged voltage curve of the slowing down engine speed standard voltage circuit with the angine speed voltage signal and detects whether the speed is above or below the specified speed
2Getting the signal from the comparator, the flame-out circuit turns ONOFF the transistor (TR) and controls the thyrister gate
3The slowing down engine speed standard voltage stabilizes at the preset stable engine speed and flaming-out and firing are