Paul not sure what has happened, are you sure it won't rotate, pull the plug out and see if that is the problem, remember you are trying to rotate the motor using a much smaller circumference than turning it using the blade carrier. Then comes my next question, why do you want to remove the boss if you just want to change the blade carrier. The boss is the same since I think back in the seventies, might have been back in the late sixties. Only ones that are different are the ones they fitted 4 strokes on Victa bases
