The 21-year-old Old Trafford academy graduate has joined the Seasiders following a successful six-week trial.
Marsh was released by the Premier League champions back in June.
Meanwhile, manager Simon Grayson has revealed he missed out on a couple of transfer deals leading up to the close of the window on Friday.
"I have said on a number of occasions I will not sign players for the sake of it they have to add something to our squad," he said.
"We were close to completing a couple of deals on Friday but for various reasons they didn't happen."