It could be seven years’ detention for a Waterfront Commission cop who cheated on his detective’s exam.

That’s how much prison time James Sutera is facing for allegedly lying to investigators who were looking into corruption on the waterfront.

Sutera, 28, had no law-enforcement experience whatsoever when he was hired in 2007 on the order of Michael Madonna, then the New Jersey commissioner for the Waterfront Commission of New York Harbor, and a friend of a friend of Sutera’s, prosecutors said yesterday.

He flunked his written test for the job twice, Manhattan DA Robert Morgenthau said. Madonna pulled some strings for Sutera to take the test a third time — and slipped him a copy of the answers. Sutera then aced the test.