Ben Stiller has won the hearts of many by playing various endearing schlubs. And what could be more endearing than a schlub trying to pick up a strange woman while on his honeymoon?

The Farrelly brothers’ new film, “The Heartbreak Kid,” trades on Mr. Stiller’s trustworthy persona to mine honeymoon adultery for laughs. But where such Farrelly films as “There’s Something About Mary” and “Kingpin” built shock humor on the premise of good intentions, the shallow premise of “The Heartbreak Kid” is accompanied by mostly rote comedic attempts.

Mr. Stiller plays Eddie, the owner of a sporting goods store whose fear of commitment is supposedly ruining his life. Amid vague pressure from his unhappily married friend Mac (Rob Corddry) and his smarmy widowed father (Jerry Stiller), Eddie meets Lila (Malin Akerman), a beautiful blonde who gets mugged during their meet-cute. After dating a short time, Lila tells Eddie that she is being relocated to Rotterdam, and the impending move turns out to be just the motivation Eddie needs to propose.

Their whirlwind romance culminates in a quick wedding and a road trip to Mexico for their honeymoon. Shortly into their trip, Eddie realizes that Lila is not the girl he thought she was. His wife’s incessant singing, former drug problem, and aggressive sexual inclinations make him rethink not his own superficiality but his decision to wed her.

Shortly after his big realization, Eddie meets Miranda (Michelle Monaghan), a lacrosse coach visiting Mexico for a family reunion. The main distinction of note between these two seems to be hair color — both are sweet, cute, and bland. Lila suffers some major indignities at the hands of the writers, but Ms. Akerman survives most of these with grace and charm, perhaps the biggest feat of the film.

The Farrelly brothers’ films often treat women like scenery, but the insulting premise here — that attractive women are interchangeable — is less than charming. Strangely, the lifetime commitment that Eddie has made to Lily is enough to convince him that Miranda is his true love — though she is just as likely to reveal quirks that will convince him otherwise later on.

Ms. Monaghan is adorable enough, but her character is far too thinly drawn to justify Eddie’s instant attachment to her. And Mr. Stiller, who once again reprises the role of the loveable, accident-prone imp that brought him and the Farrelly brothers success almost prevails over the inherent unctuousness of the plot.

But even Mr. Stiller’s disarming appeal cannot overcome the fact that Eddie is mostly a manipulative idiot. And other than Ms. Akerman, the supporting characters are not quirky or likable enough to distract from the flawed premise. Mr. Stiller’s father makes an uncharacteristically terrible impression as Eddie’s oversexed and badly dyed father, while the comedian Carlos Mencia makes for an insulting Mexican with a terrible fake tan. The majority of Miranda’s supposedly lovable family just takes up space.

The Farrelly brothers set a gross-out humor precedent in romantic comedy when Cameron Diaz opened the door in “There’s Something About Mary” and put Mr. Stiller’s protein shake in her hair. But cringe-inducing humor has become an expected nuisance in such films, and the brothers’ endeavors here are neither inspired nor particularly funny.

There are plenty of moments of levity in the first act, but too much of what’s presented looks like a Farrelly rehash. Scenes involving foreign objects stuck up Lila’s deviated septum are nearly as painful to sit through as they would be to experience. Her ravenous sexual appetite garners some laughs, but by the time the Farrellys expose her disturbingly decorated privates, the film has gone thoroughly off its rails. The people sitting next to me were smart to leave by this point, but the directors pounded out another 30 minutes of insult humor before letting the credits role, sending Mr. Stiller on an ill-advised adventure across the Mexican border in search of love. Focusing a film on embarrassing, cringe-inducing antics backfires when the audience no longer cares about the emotional arc of the plot. Plenty of other films have struck box office gold by physically abusing the diminutive Mr. Stiller on celluloid. But falling short of finishing him off entirely, the violence against him here is just an irritating tease.

mkeane@nysun.com