Jdollar

I'm new to this forum, so I'm sure this question has been asked before. I apologize in advance. I live on a private Lake in central California. Lake is approximately 30-40 acres and depth ranges from 10' deep to 40'. It was built on an old sand pit, and there is not much structure other than weed lines. We catch a lot of fish every time we go out, but they're typically 1-2lbs. Biggest fish so far is 8lbs. I know there are double digit fish in this lake, and I just can't figure out how to catch them. Any suggestions?