"At the beginning of the year, we had a goal and that was to get back to the state championship," said Johnson, who had 22 points, 10 rebounds, and five assists.
The Aces closed the first half on a 14-2 run at soldout Williamsport High School and went ahead at halftime on JaQuan Johnson's coast-to-coast layup.
New Castle used an 11-0 run late in the third quarter to tie the score at 43, but Lower Merion scored the quarter's final four points and never trailed again.
Dalembert scored 15 points, grabbed 15 rebounds, and blocked four shots..
Raheem Hall added 13 points, and B.J. Johnson's defense started changing the game's complexion in the second quarter.
"Going to back-to-back state [finals] is an awesome accomplishment and really difficult," Lower Merion coach Gregg Downer said. "We made a run, they made a run, but the kids certainly didn't panic."
Lower Merion gets another shot at Chester after losing in last year's state final and this season's District 1 final.
"I think we have one of the more talented starting fives and benches in the state," B.J. Johnson said. "Whenever we play well together, we succeed."
New Castle 15 13 15 20 – 63
Lower Merion 11 18 18 20 – 67
NC: Malik Hooker 19, Shawn Anderson 17, Brandon Domenick 7, Anthony Richards 8, Antonio Rudolph 9, Drew Allen 3.
LM: B.J. Johnson 22, Yohanny Dalembert 15, Justin McFadden 4, Raheem Hall 13, JaQuan Johnson 12, Corey Sherman 1.