After serving for 38 years on town boards and committees, Selectman Kevin Donovan said he is done and will not run for re-election. Donovan said he had decided to serve his current three-year term in part to help with the town’s 350th celebration. “It’s time,” Donovan said in an interview. Donovan, who is the chief executive officer of the South Shore Tri-Town Development Corp., said he has also served as town moderator, chairman of the Police Station Building Committee, and on the sewer commission and a personnel bylaw committee. Kenneth Coyle, the other selectman whose term is up this year, has taken out papers to run in the April 26 town election. Also running is Maureen Jansen, chair of the Finance Committee, who resigned to run for the Board of Selectmen.