Saints led by three goals at the break against their fourth-tier opponents thanks to goals from Adam Lallana, Jason Puncheon and Morgan Schneiderlin.
But it was in the second period that things really came to life, with Guly's excellent treble being sandwiched by a Jay Rodriguez penalty on the hour and and Luke Shaw's deflected strike five minutes from time.
Saints found themselves on top right from the off, and could well have gone ahead inside two minutes when Puncheon's dinked cross found Rickie Lambert, but the striker's headed effort went over the bar.
The opener did arrive with eleven on the clock as Lloyd Isgrove did well to burst forward then play a perfectly-weighted pass to allow LALLANA to finish past Palamós goalkeeper Bayona with ease.
The hosts did have an immediate chance to equalise, though, as Iván Díaz played in Dani Fernández but Artur Boruc was relatively untroubled.
Instead it was Saints who scored the second of the game soon afterwards, as Danny Fox's cross-field pass found PUNCHEON, who slammed inside the near post after cutting onto his left.
Puncheon then curled wide of the far stick as his side went in search of a third, before another chance fell Fernández's way only for him to find Boruc in top form.
The Saints goalkeeper had to deny the lively Fernández once more midway through the half, saving well with an outstretched leg.
The visitors had the ball in the net for a third time on 23 minutes as Isgrove bundled home off a defender only to be penalised for a push.
Puncheon then hit the post after collecting an excellent long pass from Calum Chambers, before Palamós 'keeper Bayona pulled off a good stop to parry a Schneiderlin drive.
SCHNEIDERLIN could not be denied soon afterwards, though, as some good play involving Jack Cork and Puncheon found the Frenchman, who converted from a tight angle on 36 minutes to bring the half to a close.
HALF TIME: PALAMÓS 0-3 SOUTHAMPTON
Manager Pochettino chose to use nine of his eleven substitutes at the break, keeping only Schneiderlin and José Fonte on the field from the first-half XI.
That meant Paulo Gazzaniga lined up in goal behind a defence made up by Fonte, Nathaniel Clyne, Jos Hooiveld and Shaw.
Schneiderlin was joined in midfield by Victor Wanyama and Steven Davis, while Rodriguez was supported up front by Guly and James Ward-Prowse.
RODRIGUEZ – who scored both goals in Wednesday's win over UE Llagostera – quickly set about adding to his pre-season tally, but saw a 48th-minute drive flash wide.
He could not be denied on the hour though as, having been tripped by substitute goalkeeper Fedir, he stepped up to slam in a penalty for four-nil.
The first of GULY's three goals arrived three minutes later as he drove a first-time effort beyond Fedir from the best part of 25 yards, and his second wasn't far behind.
Right-back Clyne did well to get down the right and hang a cross into the area, with GULY rising well at the far post to head across goal to make it six.
His ten-minute treble was complete on 72 minutes as Clyne burst down his flank once again and centred for the Brazilian to fire home from close range.
Rodriguez then fizzed a shot over Fedir's crossbar with a quarter-hour left on the clock as Saints set about trying to notch even more goals.
Their eighth would arrive five minutes from time as SHAW – by then playing on the left wing – watched his drive deflect off a defender and beyond their second substitute goalkeeper Martí Bartrina.
Overall, the home side had offered little resistance other than a decent spell around the quarter-hour mark, meaning Saints were fully deserving of their hefty winning margin.
FULL TIME: PALAMÓS 0-8 SOUTHAMPTON
Palamós team: Bayona (c) (Fedir 46 (Martí Bartrina 79)), David Malo (Neil Araujo 78), Chicho, Iván Díaz (Toni Rodríguez 66), Marc Vila (Guille 62), Maik Molist (Bachs 76), Jaume Duran (Pugui 46), Dani Fernández (Sergi Arimany 46), Bacho (Morales 46), Subi (Diego Zayas 71), Venzal (Fran Iglesias 62). Unused substitutes: Álvaro.
Saints team: Artur Boruc (Paulo Gazzaniga 46), Calum Chambers (Nathaniel Clyne 46), José Fonte (Jack Stephens 66), Dejan Lovren (Jos Hooiveld 46), Danny Fox (Luke Shaw 46), Jack Cork (Victor Wanyama 46), Morgan Schneiderlin (Lloyd Isgrove 66 (Jordan Turnbull 82)), Adam Lallana (c) (Steven Davis 46), Lloyd Isgrove (James Ward-Prowse 46), Jason Puncheon (Guly 46), Rickie Lambert (Jay Rodriguez 46).
Goals: Adam Lallana (11), Jason Puncheon (14), Morgan Schneiderlin (36), Jay Rodriguez (pen 60), Guly (63, 65 & 72), Luke Shaw (85)