One of the great mysteries of movies is how ideas get carried from one point to another. Refining the last statement would be how good ideas turn into bad ones. In the case of “Bad Boys II,” it’s how a good idea goes from a comedic buddy cop movie to the painful experience of watching a truly awful film.

“Bad Boys II,” a loud, entertaining and above all, frantic mess, steers in more directions than one of its numerous drunken car chases. At such a whopping runtime, it amounts to absolutely nothing more than the thinly veiled, overproduced jumble lying underneath all of its violence and gross-out laughs.

Returning to their roles, Martin Lawrence and Will Smith respectively star as the nervous Marcus and the suave Mike. Again caught up in a silly, impossible situation that any cop — combined with years of experience — would never dream of encountering, the two cops/best friends dodge bullets and bravely shoot their way out of any problem.

Syd (Gabrielle Union of “Bring It On”) is Marcus’s younger sister who’s not only in town to visit, but to continue her undercover delving into the underworld of Miami’s ecstasy cartel headed by Johnny Tapia (Jordi Molla). The three get tangled in investigation: Syd as the smooth-operating DEA agent with Marcus and Mike backing her up as the James Bond-style cops.

A movie like “Bad Boys II” obviously surrenders any believability. In a way, it’s what makes parts of it likable. The laughable situations, plot conveniences and choppy editing work in movies like this — mixed with over-the-top, extended shoot-outs and chases with an undeniable chemistry between its two stars.

In a brand similar to the Mel Gibson-Danny Glover team of the “Lethal Weapon” series, Lawrence and Smith share a presence on screen so comfortable it’s hard to believe a camera is necessary.

What makes Gibson and Glover so enjoyable to watch is their constant pranks and antics against each other. The two-Stooge gag works there, but here it seems Lawrence and Smith are on the verge of laughing at their own jokes.

All things aside, “Bad Boys II” starts off promisingly. The 147-minute (yikes) sequel (double yikes) is built solely around an elaborate, stunning car chase.

The scene is fresh with its wicked camera angles, effects shots and numerous car-flippings. Trite as it is, the scene is undeniably fun to watch, mixing intensity with jolts of action extravaganza.

The intensity reminded me of the shootout/chase scene in “Heat” — the only difference is the action scene in “Bad Boys II” blows hurricane winds in comparison.

No matter how satisfying the initial chase sequence is, it far from makes up for the rest of the movie’s shortcomings. When the chase sequences and shootouts, each one of them filled to the brim with humorous (although shallow) tidbits begin to consume scene after scene, new chapters begin to feel weary and increasingly thin.

Eventually, “Bad Boys II” forgets the slaphappy action movie it is. It fails to realize the number of bullets shot, bodies blown up and people these two cops shoot within a week all mix into a quite disturbing movie-going experience.

I realize you’re supposed to be entertained while watching this movie, and things like body count and these characters’ personal confrontation with the stressful jobs they have is meaningless — but come on — the action isn’t where it’s supposed to be; the guys are trying too hard for laughs and “Bad Boys II” is just too damned long for me to care about.

Perhaps instead of packing everything into a movie, a sequel no less, would have serviced a better outcome if the filmmakers — producer Jerry Bruckheimer and director Michael Bay of all people — did not have such a lack of respect for their audience.

If you haven’t seen any more than ten films of its genre before, you may just enjoy “Bad Boys II.” Otherwise, stick around for an hour so you can see the chase, and get out of there. Minus a few genuine laughs, trust me: You’re not missing anything — you’ve seen this routine before.