Jump into your time machine – hot tub or otherwise – and hop back to March 2010. That’s when the world was graced with the first "Hot Tub Time Machine." The ’80s nostalgia trip – complete with horrible outfits, era-appropriate tunes and John Cusack in the lead – was lewd, dumb, juvenile, technically sloppy, frantically told … and occasionally pretty funny too. Basically, for better or worse, it was a movie called "Hot Tub Time Machine."

Arriving five years later, "Hot Tub Time Machine 2" provides a pretty similar experience: messy time travel shenanigans pitching hit-or-miss riffs and jokes that top out at a serviceable batting average. It’s still lewd. It’s still dumb. It’s still technically sloppy and frantic. The big change: Cusack’s no longer with the series, seen only in old press still form.

He’s replaced by "Parks and Recreation" regular Adam Scott – and a surprisingly vulgar mean streak. In movies, time travel typically ends up in the hands of the decent or deserving. "Hot Tube Time Machine 2" proposes … what if it didn’t? What if, instead, time travel wound up in the depraved, often drug-addled hands of a bunch of unrestrained man-child ids, who then proceeded to violate space, time and everyone and everything they ran into along the way? The answer? Some laughs, I guess. A good amount of silence, too. Bags don’t come much more mixed than this.

The Hot Tub Expositional TV News Opening Montage Machine lays out what’s happened since the last soak. Crazed Lou (Rob Corddry) is one of the most powerful men in the world – both as the inventor of the Internet giant Lougle and as an ’80s hair metal icon – with the dysfunctional egomania to match. Nick (Craig Robinson) is a pop superstar, cranking out monster hit songsbefore the actual artists can dream them up, accurate lyrics, be damned (poor Lisa Loeb, doomed to a life of cat wrangling). And young Jacob (Clark Duke) is still aimless, living with pops Lou and reluctantly serving as his butler.

Things seem pretty terrific in their time-manipulated lives, but when Lou takes a shotgun blast to the … little Lous, the trio heads back to the tub to stop his unknown assailant. Instead of the past, however, the tub picks a new destination for the guys. And where we’re going … we still need roads. But hey, at least the cars are sentient and drive themselves (as long as you don’t hurt their feelings).

That’s right; it’s the future. There, Jacob is now the powerful and wealthy tech genius, while Nick’s attempt at an original song turned him into hacky dance kitsch and Lou is a strung-out, grey bearded wash-out.

After soaking in their new digs and picking up Cusack’s naively milquetoast adult son (Scott, wearing some odd future kilt), they hunt down their suspects. Perhaps it was a desperate down-on-his-luck pal (Jason Jones, one of three "Daily Show" alums here including Corddry and a timely Jessica Williams cameo)? Or Lou’s despairing genius tech department head (Kumail Nanjiani)? Or that sentient car from before?

To be fair, all of them have understandable motives for wanting to throw some shotgun shells in Lou’s direction. He’s an outrageously rude and terrible creep – his two other chums are only a little bit better, if just as self-serving – and the humor in "Hot Tub Time Machine 2" follows suit. The jokes in Josh Heald’s script are dark and bitter, running the gambit from gay panic, rape and general crassness to just plain old ruining other characters’ lives.

It’s tempting to give the movie credit for its unrepentantly crude and occasional cruel sense of humor, letting the guys’ uncontrollably self-centeredness go wild without the pleasant ’80s nostalgia glasses or a naturally earnest John Cusack straight man to soften it. It’s a movie about the inmates running the asylum, and the asylum is the space-time continuum.

If only it was more consistently funny. In addition to the vinegary meanness, a majority of the gags are tremendously dumb and cheaply vulgar. Namedropping pop culture references is a common crutch here. Some of the extended jokes, like Adam Jr. tripping on future drugs and a future truth-or-dare reality show, feel like weak versions of funnier sequences from the past ("Idiocracy" and "Get Him to The Greek" come to mind). And speaking of extended, director Steve Pink often lets his lead trio Apatow-style riff with one another for a line or two too long. Often, half of the improvised quips seem to be worth a laugh, while the other half would’ve been better suited as a deleted scenes DVD extra. 

Then again, the whole movie – and its predecessor – has that loose, slapdash vibe. Sometimes the devil-may-care adds to the easy-going nature of the film; just as often, the shaggy jokes and story drag, holding on a joke too long or going for a touch of character or emotional development that none of these callous cretins particularly earn (the first film was better at feigning human interest).

Still, despite the uneven flow and mean streak, like the Bud Light of comedies, the movie somehow goes down pretty smoothly. And, much like Bud Light, both the product and consumer have a carefree, mutually miniscule demand expected from each other and themselves. So even when it trips up or stumbles, either dramatically or comedically, "Hot Tub Time Machine 2" slides by pretty effortlessly.

Part of that vibe comes from the returning cast, who – despite playing despicable guys – are still amusing to hang with. Corddry, Robinson and Duke play off each other nicely, bouncing zingers back and forth, and entertainingly reviling one another. When the movie scores a laugh, it’s normally because of the actors’ sheer force of will, digging into the film’s giddy indecency.

And "Hot Tub Time Machine 2" does score laughs, just on a very inconsistent basis. Much like it’s namesake, the movie is a hot mess, and even with all of the bubbles, you might feel a little dirty afterwards.