Prevention is key, just like cancer. Once corrosion starts, it's way harder to deal with the problem. And, just like cancer, corrosion can take over and destroy!
Key for saltwater use is thorough freshwater flushing with Salt-Away after each use, and then generous amounts of anti-corrosive treatments, like LPS, Bullfrog, Wd-40, the list goes on and on...
I've found that Wd-40 works really good and is cheap, so I can apply it liberally on a very regular basis, and it won't break the bank.
With corrosion, a key thing to remember is that moisture is the enemy, so keep the moisture out of the engine compartments, etc. There are moisture absorbing cups that you can get at a marine store that will draw moisture from the air and put it in a liquid/gel form inside the cup, which you later can dump out.
Wash, Wash, Wash, then lube everything up, and you'll be fine. Just look at how many fishing boats are out there, they all aren't self-destructing. Key ingredient is lots of love, don't slack on the maintenance or you will feel the effects real quick!