A quiet encounter looked set to be heading for a goalless conclusion until the Spanish midfielder netted his first goal in English football by converting a corner, and cruelly denying the Eagles what would have been a well-deserved and hard-earned point.
Boosted by their win against Chelsea a week ago, Palace looked the better team during an edgy first-half, which saw little goalmouth action, although like against Blues the unorthodox strike partnership of Wilfried Zaha and Andros Townsend’s pace caused the home defence problems throughout the opening 45 minutes.
However shots at goal were few and far between early on, with the first attempt seeing Zaha passing tamely at Rob Elliot from a tight angle on 23 minutes, but then not long after Jeffrey Schlupp miscued and Matt Richie saw a goalbound effort crucially strike Mamadou Sakho and deflect wide as the game began to bubble.
Things then boiled over when a strong challenge from Yohan Cabaye on DeAndre Yedlin saw a number of players from both sides get involved in some argy-bargy, for which the Frenchman was booked, but that helped bring the game to life and United went close to breaking the deadlock when Christian Atsu shrugged off Joel Ward and got into the box before blasting into the side-netting.
It was then rippled at the other end when Townsend and Zaha combined to give the latter a sniff of goal as he peeled away at the back post but headed wide of the mark, however Hodgson would have been pleased with what he saw from his side as they made their way back to the changing room at the break.
Once again, there was a lack of action straight after kick-off as conditions worsened and the rain fell, but despite being jeered on his first return to St James’ Park since his departure to Palace Townsend continued to look dangerous and bent a shot over Elliot’ crossbar just after the hour mark.
The visitors had quietened the 52,000 in attendance but as the half progressed Newcastle began to create more chances and Julian Speroni was called into action twice within 60 seconds when he dived to catch a curling Mohamed Diame shot, and then fisted away a fizzing Jonjo Shelvey piledriver which swerved through the air in the blustery conditions.
The game remained on a knife-edge and Palace nearly snatched the opener with 10 minutes remaining when Schlupp slipped in Ruben Loftus-Cheek, and he sent a cross-shot towards the back post that looked set to be converted by Patrick van Aanholt, but the Dutchman failed to make contact by the length of a stud.
And that miss proved costly as five minutes later, the Magpies took the lead. Richie fired a corner into the box which was raced onto by substitute Merino, and he got up above James McArthur to head past Speroni and ensure the Eagles returned to south London without the point they deserved.
Newcastle: Elliot, Yedlin, Lascelles, Lejeune, Manquillo, Richie, Hayden (Merino 56), Shelvey, Atsu, Perez (Diame 65), Joselu (Mitrovic 78). Subs not used: Darlow, Gamez, Clark, Murphy.
Palace: Speroni, Ward, Dann, Sakho, Van Aanholt, McArthur (Sako 87), Cabaye, Milivojevic, Schlupp, Townsend, Zaha (Loftus-Cheek 77). Subs not used: Hennessey, Riedewald, Fosu-Mensah, Tomkins, Puncheon.