Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 206Get this manual
HONDA BFSOA25A
2) Operation
The comparator circuit compares the condenser discharged voltage curve of the slowing down engine speed standard voltage circuit with the engien speed voltage signal and it detects whether the speed is above or below the specified speed
2) Getting the signal from the comparator, the flame-out circuit turns the transistor (TR) ON or OFF and controls the thyrister
3)The slowing down engine speed standard voltage stabilizes at preset voltage in accordance with the stable engine
speed and flaming-out and firing are repeated at this stable engine speed