The Pilgrims, who scored four against Fleetwood last weekend, romped to victory with former Shrimps striker Lewis Alessandra scoring two of the quintet.
Argyle's bright start was rewarded when right wing-back Durrell Berry fired them ahead in the fifth minute after Morecambe goalkeeper Barry Roche could only parry Matt Parsons' thumping drive. It was Berry's first ever Football League goal on his 97th Argyle appearance.
Alessandra made it 2-0 five minutes before the break with a cool, clinical finish after being put through on goal by skipper Conor Hourihane. The captain set up the goal after dispossessing Morecambe's Sean Beeley in midfield and then sending an inch-perfect pass into striker Alessandra's path.
Tyler Harvey forced Roche to make a good save on 76 minutes following a defence-splitting run from the teenage substitute but the stopper would be picking the ball out of his net again, central defender Curtis Nelson heading in Luke Young's corner.
Substitute Andres Gurrieri started and finished a sweeping length-of-the-field move to put further gloss on Argyle's victory three minutes from the end, and Alessandra claimed his 12th goal of the season with a stoppage-time fifth for Sheridan's men.