A Brad Groves strike on 34? minutes separated the two teams with Abbas Saad?s men taking the game to their more illustrious opponents from the outset.
Manly should have taken the lead midway through the first-half after Craig Midgley and Robbie Cattanach both hit the crossbar from point-blank range following a teasing ball via Joey Schirripa from the left-flank.
Nine minutes later, Groves had the northern beaches faithful on their feet after he rifled home a free kick from 25-yards past Chad Taylor.
Erick Anabalon tested Brad Swancott with his own free-kick on 40? minutes with the custodian doing well to keep out Devrim Huseyin?s follow-up effort.
Dusan Mihajlovic, returning after an extensive injury lay-off, went within a whisker of doubling Manly?s lead on the stroke of half-time but headed his half-chance over the crossbar.
Penrith came out in a determined mood after the break and Nathan Ralph went within centimetres of squaring the ledger on 50? minutes.
After turning Adam Israel inside out, the winger shot on the turn and slammed his effort over the crossbar.
Team-mate Jason Brown followed suit sixty seconds later after seeing his goal-bound strike take a deflection and sail out for a corner.
On the hour mark some enterprising passing from Phil Moss? men almost saw a second goal.
Mihajlovic, Cameron Jones, Groves and Schirripa all combined well before Groves ran to the byline and delivered a perfect ball into the path of Michael Williams who snatched at the chance and volleyed over.
Schirripa then unlocked the Penrith defence with ten minutes on the clock after playing Midgley into space but the Englishman blazed over after attempting to lob Taylor from the edge of the area.
Former Manly representative Stewart Van Bentum, who caused a few headaches down the left wing after replacing Michael Cromar, went close for Penrith on 83? minutes after his speculative effort was tipped over the crossbar to safety by Swancott.
Panny Nikas went within inches of snaring a deserved equaliser seconds later.
After beating two defenders, Nikas drilled his shot across Swancott?s body only to see his strike cannon off the left post and back into play.
Midgley should have wrapped up the three points in injury-time after cutting inside his defender but produced a woeful strike from six-yards that summed up Manly?s afternoon.
Penrith coach Abbas Saad lamented his team?s luck but was delighted with their fighting spirit:
?We created enough chances to win the game but weren?t clinical enough,? he said.
?At times our final pass let us down and their keeper also produced a number of key saves.
?I thought Panny Nikas and Nathan Ralph were outstanding for us, they held their own.
?If we can play like that until the end of the season I will be a happy man.?
Phil Moss was relieved to see his team?s hoodoo end at home, after four losses and a draw in their last five outings:
?The most important thing today was that we got a win at home,? he said.
?Penrith sat back and looked to get us on the counter and I thought they played very well.
?We are coming out of a rut and I can see us improving, which is a good sign heading into the finals.
?I am still looking for the right mix in terms of our starting team because at the moment not enough players are putting their hand up to be picked week in, week out.
?We need the right balance and chemistry to move forward and with the Sydney FC trial game on Wednesday night I am hoping that will give the boys the shot of intensity they need.?
Manly United FC 1 (Brad Groves 34?)
Penrith-Nepean United 0
Venue: Cromer Park
Referee: Kris Griffith Jones
Assistant Referees: Daniel Dewhurst and Nick Backo
Crowd: 500 (approx)
Manly United FC: 1.Brad SWANCOTT; 2. Adam ISRAEL , 3. Andrew MAILER, 6. Brad GROVES , 8. Michael WILLIAMS, (4. Roberto HAMAD 77?) 9. Robbie CATTANACH, 10. Dusan MIHAJLOVIC, (14. Caetano LIMA 71?) 11. Craig MIDGLEY, 15. Cameron JONES, (19. Richie WILLIAMS 64?) 16. Joey SCHIRRIPA, 18. Beau BUSCH
Substitutes Not Used: 12. Chris PAYNE, 20. Rhyss KEANE (RGK)
Yellow Cards: Nil
Red Cards: Nil
Penrith-Nepean United: 1. Chad TAYLOR; 15. Ben WRIGHT, 9. Carl McNAUGHTON, 23. Devrim HUSEYIN, 11. Erick ANABALON, 5. Luke BOYD, (4. Ryan O?SHEA 51?) 16. Michael CROMAR, (8. Stewart VAN BENTUM 70?) 13. Nathan RALPH, 2. William STUART, 29. Panny NIKAS, 6. Jason BROWN (3. Chris GOMEZ 53?)
Substitutes Not Used: 28.Yianni FRAGOGIANNIS, 42.Daniel SCHWARZER (RGK)
Yellow Cards: Nil
Red Cards: Nil
3 ? Brad Groves (MU)
2 – Adam Israel (MU)
1 – Panny Nikas (PNU)
-By Andrew Prentice