This feat comes from the F13 novel Hell Lake novel, which has been accepted as usable from this thread. The feat:
Trey took the plunge. Not even a hundred yards down the bank from both of them, he became visible to Jason at last. It was too late. The power cables he wore created an instant short circuit between the water and the electrical generator. Terrified, but determined, Trey's body began to burn. In his agony, he felt the fifty thousand volts tearing through his body keep rising, due to the catalyst of the water. His impulse to tear the cables free from his body was negated by the pain. There was nothing to do but play his part now. By the time the young man had sunk downwards into the water, his skin burned and his heart stopped by electric shock, he had set the western side of Crystal Lake on fire.
An electrical shockwave of five hundred thousand volts rippled swiftly through the water. As the burning sensation hit Gretchen, she almost passed out. Semi-conscious, she was still able to scramble toward the muddy bank, her face partly submerged in the burning fluid. But Jason had waded in deeper. He was engulfed in an erupting sheet of flame on water.
Crystal Lake began to transmogrify. It was no longer a place of fluid tranquility, or even a lake in which a massive electrical charge had sent a shock through the water. It started to burn, as if it were a solid combustible object. Jason felt the heat and started to weep silent tears. His mom had betrayed him. After all these years, after all her promises. The lake's transforming waters had not taken him back to childhood, to the days before the staff at Camp Crystal Lake left the handicapped boy to drown. They had sucked him into hell.
But this was not the chill wasteland he had grown used to, before the waters of Crystal Lake aw his second resurrection. As the water burned, so it became more solid. Its rippling textures swelled into recognizably human shapes. Where only moonlight reflections had been, there were now agonized faces. Water became fire, as if in some strange medieval act of alchemy, and Crystal Lake became a traditional medieval image of hell.
It rose to the banks with screaming, burning bodies. Trey Leblanc had been granted the mercy of death, and had long since sunk into the waters. But there were no waters now. There was only a vast mass of conjoined roasting flesh, hundreds upon hundreds of damned souls who tore at each other, or at themselves, in their agony.
This was a hellfire they had never known. Amidst all the damned who were returned to the place of their former resurrection, the immolating form of Charles Westenhaus flailed and lashed at all the other burning bodies so insufferably close, but could do nothing to alleviate his own torment.
And in the center of them all, Jason Voorhees began to feel his already rotten, fungal flesh burn away. His earthly form, so seemingly indestructible, was incinerating, melting. As he was sucked under into the pools of flame, the murderous masses he had once led clawed at him in their ingratitude, with their burning hands, until the ashes of his skin were torn from his bones.
Since he is ultimately "killed" by this, albeit after some time and with other souls trapped within the lake tearing at him, I will calc the 50,000 volt as a safe low end, and the 500,000 voltage as an upper limit.
Current = Voltage / Resistance
Watts = Voltage x Current
On average, the human body has a resistivity of 1,000 - 10,000, but I'll use the 300 value provided here since Jason is engulfed in water. And resistivity lowers with wetness.
50,000 Volts / 300 Ohms = 166.67 amps
50,000(166.67) = 8,333,000 J (9B) but 75% of Wall+ and nearly 44x the accepted 9B boiler feat Jason is currently scaled off of.
Now for what "kills" him.
500,000 / 300 = 1666.67
500,000 x 1666.67 = 833,335,000 (9A+), or 1.5x the 533,460,000 9A+ value.