After eight years on the job, Selectman Richard Powell resigned Tuesday so that he can apply for the town administrator job vacated in February by Benjamin Puritz. The town is working with the Edward J. Collins Jr. Center for Public Management at UMass Boston on recruitment, and applications are due Friday. Asked in a telephone interview why he decided to apply, Powell said he enjoys local government and would like to do more. “It’s really a full-time job, and I’d like to engage with the town full time,” he said. Powell is a lawyer and has worked for about nine years as chief of staff for state Senator Cynthia Creem, a Newton Democrat. Previously, he was a legislative aide for then-state senator William Keating, who is now a US representative, and for Creem. State conflict-of-interest law prevents a selectman from being appointed to another paid position. The remaining year of Powell’s term will probably be filled in the May 20 annual election. At least one person, former School Committee member Mitchell Blaustein, has expressed interest in running.