Special Town Meeting last week shot down a proposed rule change that would have allowed recent members of most town boards to become Cohasset town manager without delay. The vote was 188 to 158 against the proposal. Current rules prohibit anyone from being appointed town manager if he or she has served on any elected or appointed town board within the previous year. The proposed change would have applied the prohibition only to selectmen, for a period of 15 months. Selectman Chairman Paul Carlson said the vote has no impact on Acting Town Manager Michael Milanoski’s current contract, which expires June 30, 2013. Milanoski had served on two appointed town boards in the prohibited time period.