Here's some interesting trivia about airplane engines. From Pratt and Whitney, the -15/15a, 217, 219 denotes the thrust rating. So a B-727 engine produces about 15,000 lbs of thrust and is denoted as a JT8D-15. The MD-80's use a bigger version of the JT8D and it was designated a JT8D-219 which denoted 21,000 lbs of thrust. So three engines on a 727 produced 45,000 lbs of thrust and two engines on a MD-80 produced 42,000 lbs of thrust. I don't know the vessel weight off the top of my head but I'm sure it can be looked up.
On the high by-pass engines on the B757 (that used P&W engines), the first number denoted the engine family. These were 2000 series engines. The next number denoted the airframe manufacturer. In this case the number was a 0 which denoted Boeing. The last two numbers were the thrust rating of 37 which denotes 37,000 lbs of thrust. So a Boeing B757 would be equipped with a PW 2037. The B757 was unique in that it was a grossly overpowered narrow body jet. I loved them. Boeing tried to replace them with the B737 in numerous configurations but the 737 simply doesn't have the power that the 757 had.
If a P&W is hung on a MD-11 then they'd use a 4000 series engine making about 60,000 lbs of thrust. That engine designation would be a 4460 since the airframe is represented by a 4 for McDonnell-Douglas.
Airbus engine code is 1 so the engine would be a 4157/4160 or some variant thereabouts.
So no, one 2037 engine on a B757 does not make more power than three JT8D-15 engines on a 727. The most powerful B757 that I've seen was equipped with 2040 engines so even those were a few hundred pounds of thrust short of a 727. They're still quite impressive.