question for the gurus on an evinrude 55hp

i have a 1979 evinrude 55 hp model # 55974c just put on the aluminium bass tracker for a friend runs great so far on the hose but when the throttle controler tuches the side of the aluminum boat it sparks so im backfeeding power thru my controller i would say . so i checked all the wires and they look fine on the harnes of the motor and the controller . my question is what would be causeing this problem that you could think of thanks guys i appriciate any advice you might have

bump

Check the wires in the control box to make sure you are not supplying a path to ground.