You need so much more coverage on this. Octillery has a jaw-droppingly large movepool, so abuse that!
Octozooka's crap. The irony of it all is that this accuracy-reducing move, only has 85 accuracy. Octozooka's mediocre, so surf's up, dudes! (lame pun, I know. xD)
Ice beam is great, and if you had Charge Beam on it, you'd have a makeshift BoltBeam combo, which gives fair coverage against every known type combination that is currently in the game (except for Shedinja). The passive Special Attack bonus is a major plus. Replace Signal Beam for Charge Beam.
Energy Ball is no longer needed, seeing as ground and Rock types are handled by Surf, and Charge Beam has Water covered. You could replace Energy Ball with something strong like Flamethrower to hit Steel, Bug, Grass, and Ice-types.
This gives coverage against ANY Pokemon in Pokemon HeartGold & Soulsilver. If it has a weakness, then chances are, Octillery can handle it. Psychic, Ghost, Dark, and Fighting are the only that are not covered, but you r attacks and raw stats are good enough to deal with them in no time.