Overload weapons will cause electrical damage to the targets powerplant. It has the same effect as though the target had fired a lot of energy weapons, increasing heat to degrade their MV and TR until the overload is dissipated.
Using energy weapons causes your engine to overload, which will eventually cause MV and TR penalties. An energy weapon causes its DC + BV in overload points, per shot (or burst). This is modified in the following ways:
- Triple for a HYPER weapon
- Double for a BLAST weapon
- Quartered for each scale the mecha is larger than the weapon
- Halved if the mecha has a High Output engine
- The size of the mecha is subtracted from the overload at this point
Each mecha has a capacity of its size * 10 overload before it starts losing MV and TR. A large, high-output mecha can fire a Heavy Laser Cannon for quite some time, but a small mecha with a normal engine will start overheating after just a few shots of the same weapon. Each 10 points of overload over the mecha's capacity will cause a penalty of -1 to MV and TR, starting at 15 overload over capacity for a -1.
A mecha will lose 1 overload point for every 10 seconds of game-time that pass. Note that melee energy weapons will overload, too, so you'll only get a handful of swings with that energy scythe before your mecha starts boiling.
Weapons that cause OVERLOAD will overheat your opponent's mecha if you hit, but first there is a defense roll of their Electronic Warfare skill against your Electronic Warfare skill. If you beat your opponent's roll, then you add the weapons DC, plus 1d(DC), plus (1/3 of the amount you beat your opponent's Electronic Warfare skill by), plus 5.
In other words, a single hit by an OVERLOAD weapon isn't nearly enough to overload your opponent. An average roll when you barely beat your opponent with the largest OVERLOAD weapon available, the Superheavy Particle Cannon (DC 13, OVERLOAD) will cause 13 + 7.5 + 0 + 5 = 25 points of Overload. If your opponent isn't overloaded at all, then it will take 3-4 hits to overload them. If your opponent is already overloaded, then this will cause 2-3 more points of penalty to their MV and TR.
Of course, by the time you can mount Superheavy Particle Cannons, you have much better weapons available to you, which can reduce some mecha to scrap in a few hits. Like most status ailments, this weapon is more effective when used against you than when used by you. When you're facing down a half-dozen mecha by yourself, who cares that one of them is overloaded?