In a small bowl, mix together soy sauce, sherry, sugar, and ginger. Add chicken livers and marinate, tossing occasionally, for at least 15 minutes at room temperater, or up to 4 hours in the refrigerator.
Remove livers from marinade, and drain. Press a piece of liver around a piece of water chestnut. Wrap with a piece of scallion and bacon and secure with a wooden toothpick.
Preheat the boiler. Broil the rumaki about 5 minutes from the heat, turning once, until bacon is crisp, 10 to 15 minutes.