Morton striker Peter Weatherson struck twice within three minutes to dump Gretna out of the Scottish Cup at Palmerston.

Morton keeper David McGurn kept his side in the fourth-round replay and they never looked back after Weatherson volleyed them ahead midway through the second half.

The striker added a brilliant second and Chris Millar piled on the embarrassment for the Clydesdale Bank Premier League side.

Gretna had squandered a two-goal lead against the Irn-Bru Division One side at Cappielow and their defeat ends the prospect of a fifth-round derby against Queen of the South.

The match went ahead at the second attempt after it was moved from Fir Park to the ground of Queens, who now travel to Greenock on Saturday.

Gretna, who brought in Henry Makinwa for the injured Fabian Yantorno, only briefly looked a division above their opponents and Morton could have added to their lead in the closing stages.

Morton had lost 2-0 to Dunfermline on Saturday as Gretna's clash at Hibernian was postponed and Jim McInally freshened up his side with the introduction of strikers Brian Graham and Weatherson.

Midfielder Ryan McGuffie, who scored Gretna's goal in their 2006 final defeat by Hearts, had a powerful volley blocked in the opening moments but the game started slowly.

Gretna had their first shooting opportunity in the 12th minute but Makinwa's first touch was poor and his shot was just as bad as it bobbled well wide from 20 yards.

Kenny Deuchar beat McGurn to a free-kick floated to the six-yard box by Allan Jenkins, but the striker's header drifted just wide.

The SPL side started to dominate and McGurn touched over Gavin Skelton's 10-yard strike after Makinwa's cutback.

Deuchar won Mickael Buscher's corner but his header was deflected and then touched over by McGurn, who got down to save Buscher's curling effort following the next corner.

McGurn saved the Greenock side again when he came off his line to block from Paul Murray after Deuchar had flicked on a long free-kick.

Morton steadied the ship and Graham had a 20-yard snapshot comfortably saved by Tony Caig before the Gretna keeper pulled off a superb diving stop from the same player.

McGuffie's through ball found the striker unmarked on the edge of the box, but Caig pushed wide his attempt to steer the ball into the bottom corner.

Morton created a gilt-edged chance three minutes after the break when McGuffie headed Kevin Finlayson's cross into the path of Weatherson, but the striker flicked a first-time effort over from 12 yards.

Deuchar was too high with a long-range strike and a header from Kyle Naughton's cross before Scott McLaughlin's 25-yard effort skidded just wide of Caig's goal as heavy rain began to fall.

Deuchar came closer on the hour mark when he headed against the inside of the post after another accurate delivery from the left-back.

But Weatherson gave Morton a 68th-minute lead when his volley was too strong for Caig to keep out after a long free-kick fell to his feet 16 yards from goal.

Weatherson doubled his tally three minutes later when he arrowed a 25-yard shot into the bottom corner.

The underdogs continued to look dangerous and sub Russell took the ball round Caig but was booked for diving by Kenny Clark after going down under the keeper's challenge.

Chris Millar notched the third in the 79th minute when he slotted the ball into the corner after running on to Russell's lay-off.

Jim McAlister almost added insult to injury with an excellent run and shot that was parried wide by Caig in the final minute.

Teams:

Gretna Caig, Hall, Collin, Innes, Naughton, Jenkins, Murray (McGill 74), Skelton, Buscher, Deuchar, Makinwa (Deverdics 56).

Subs Not Used: Fleming, Canning, Kissock.

Booked: Buscher.

Morton McGurn, Millar, Greacen, Harding, Smith (MacGregor 89),Finlayson, McLaughlin, McGuffie, McAlistair, Weatherson (Stevenson 85), Graham (Russell 58).

Subs Not Used: Robinson, McGeogh.

Booked: Russell.

Goals: Weatherson 67, 70, Millar 78.

Att: 1,167

Ref: K Clark (Scotland).