No way. NO BLOODY WAY. The only reason to even use pikachu is to give him a Light Ball.
PIKACHU @ Light Ball
Static
- Thunderbolt
- Surf
- Substitute/HP Ice/Grass
- Encore/Substitute
The Light Ball doubles Pikachu's Sp.Atk. That would give him the Sp.Atk and Speed of a Kyogre, which is something...Just Sub, Encore then Thunderbolt stuff, and Surf ground types. HP Grass is of course for Swampert. IMO, just switch when you see Swampert as you won't survive a hit from him and you certainly won't OHKO him.
Tested stuff, the max stats of a Pikachu with a Light Ball are only with less then 10 smaller that Kyogre's (Sp.Atk and Spd.)