We couldn't think of a better authority to field your questions on sportfishing than our own Fishing Editor Ken Schultz. Because of Ken's busy schedule, the volume of questions, and the fact that he's out fishing a lot, he cannot reply personally nor answer every question. Perhaps your topic is already covered. Ken will answer a number of questions here each week, and some will be answered in the magazine between March and August.
Manufacturers usually provide a range of line strengths that they recommend for a reel.
The problem with using a line heavier than what is recommended is that you may have diminished line capacity due to a usually larger diameter, and the thicker line may not lay well on the spool, which means that it can balloon off, cause diminished casting distance, and be generally more problematic to use. On the other hand, if you move up to a heavier line than is recommended, but use a type or brand that has a diameter that is equivalent to what is recommended for the reel, then there may not be casting issues to deal with, and you merely need to be sure that you aren't overpowering the strength components of the reel. There are so many spinning reels out that I have trouble telling the difference between them. The larger and stronger the fish, the stronger the tackle necessary for beginners, until you get the experience to use lighter gear. Small fish, few obstructions, and clear water usually are suitable for lighter tackle.