Rockfish, I would agree with what others have already said, it sounds like you're trolling to fast or don't have a big enough downrigger weight, or both. I think a 10 lbs. weight at 2.5-3kts. and 90 ft. of cable should get you to 80 feet.
I would also suggest artificials, especially if you do have to troll fast, I like to stack a couple plugs (Tomic white/green back) on 1 side and spoons on the other (Coyote's, Apex's, Superiors) you cannot troll hardware to fast, especially plugs, I've watched commercial trollers troll at 5-6 kts.
Last tip and I think probably the most important, keep your gear within 10-15 feet of the bottom, mature kings can be found anywhere throughout the water column, blackmouth on the other hand are predominantly on the bottom. I hope this helps a little, good fishin