Pompey’s run of draws continued as Morecambe twice fought back from behind to earn a share of the spoils.
Jake Jervis had put the Blues ahead with close range finishes on both occasions at a wet and windy Globe Arena.
But Mark Hughes’ header first drew the Shrimps level before Padraig Amond saw his penalty saved by Trevor Carson.
The keeper was at fault for Morecambe’s second goal, however, as he allowed Jack Redshaw’s shot to slip through his fingers.
Richie Barker made two changes from the side that drew with Mansfield the previous week.
Jervis came in for Patrick Agyemang up front for his first start since returning to the Blues earlier this month.
There was also a place in midfield for Romain Padovani, replacing the injured Simon Ferry (hamstring) with Nicky Shorey taking the captain’s armband.
Recent heavy rain meant the pitch resembled a cross between a mudbath and a sandpit, while a strong wind also hampered both sides.
But Pompey did find some early joy out wide and Sonny Bradley fired over after a corner had been only partially cleared.
And the Blues broke the deadlock on 10 minutes when Jed Wallace’s low cross from the left was flicked home by JERVIS.
Morecambe came close to an immediate leveller, but Andrew Fleming could only find the side netting after breaking into the box.
The hosts applied plenty of pressure as the half progressed, but the Pompey back-line were heading everything clear.
That was until the 21st minute when Jamie Devitt’s ball into the box was met by Hughes, whose header went in off the underside of the crossbar.
And the grey clouds chose that moment to dump their load onto the pitch below, to make the already tough conditions even worse.
Pompey created a decent opening on 30 minutes, however, when Jervis stayed onside to collect Wes Fogden’s pass and send a low cross into the ball.
Wallace steamed in to meet it at the far post, but Shrimps keeper Barry Roche bravely saved at the teenager’s feet.
It was Morecambe who should have gone in ahead at the break, though, after being awarded a penalty on 38 minutes.
Amond went down under Bradley’s challenge and, after spotting the linesman flag, referee Andy Haines pointed to the spot.
It was Amond who stepped up to take it, but his penalty was only just left of centre and Carson was able to push the ball clear.
And it soon got even better for Pompey as JERVIS grabbed his second goal of the afternoon to secure an interval advantage.
The striker was well placed to tap the ball over the line after Marcos Painter had collected Shorey’s pass and sent a low cross into the box.
Half Time: Morecambe 1 Pompey 2
The first half had been surprisingly fluid given the state of the pitch, but it was more of a scrappy affair after the restart.
Pompey, though, seemed content not to be overly adventurous as they looked to hold on their lead.
Things were understandably a little more frantic for Morecambe, but they were struggling to keep hold of possession.
There was a worrying moment when Carson failed to hold a long-range drive, although Bradley came to his keeper’s rescue and got the ball to safety.
And the 846 travelling Pompey seemed to be enjoying themselves in the away end, playing their part by producing a constant stream of noise.
Barker made his first change on 67 minutes as Wallace, who looked like he had picked up a knock, was replaced by Andy Barcham.
Pompey were looking comfortable at the back and it took an individual error to let Morecambe back into the game.
Substitute Redshaw did well to sneak in behind the Blues back-line and latch onto a long ball, but his shot was not powerfully struck and Carson should really have kept it out.
The goal seemed to spur the Shrimps on and a couple of efforts from distance flew narrowly over the bar.
Pompey threw on Agyemang for the final few minutes as they looked to grab a winner, but both sides had to settle for a point.
Morecambe (4-2-3-1): Roche; Wright, McCready, Hughes (c) (Doyle 46), Threlfall; Drummond, Kenyon; Devitt (Redshaw 59), Fleming, Ellison; Amond (Sampson 74)
Goals: Hughes 21, Redshaw 76
Subs not used: Arestidou, Diagne, McGee, Williams
Pompey (4-4-2): Carson; Alfei, Devera, Bradley, Painter; Fogden, Padovani, Shorey (c), Wallace (Barcham 67); Jervis (Agyemang 87), Taylor
Goals: Jervis 10, 43
Subs not used: Smith, N’Gala, Whatmough, Ertl, Racon
Referee: Andy Haines
Attendance: 2,550 (846 Pompey fans)