Hey. I've got a 44' steel trawler. I use 14 large aluminum plate anodes distributed about the hull and rudder, plus a zinc "baseball" around the prop shaft because no one seems to make aluminum shaft anodes. I have no pitting even where the steel has had all the paint scrapped off. My prop shaft is bonded to the engine with a brush (I have a spare if you need one). You don't have enough anodes and may be using zinc when aluminum is best for steel. When you upgrade your anodes, purchase a silver reference electrode (The anode dealers sell them for $100-$125) and keep your hull at one volt or more relative to seawater. That will tell you when you need to renew your anodes. I keep two sets of anodes, and wire brush the used set so it's ready for the next haul out. Some of mine are on their third year - you can't read the label anymore, but they are still big sheets of aluminum. Sorry you've had problems. The irony on my boat is keeping ahead of the above water rust, not the below water.