hmmm, the most important thing when we were done riding is SOAP everything down (EVERYTHING). I used to even dump a little salt away in the bilge and fill it up, then let it drain out. After that, I would spray the engine down with WD-40. I wouldn't care a bit if the engine looked like a big grease pile after a while. Who cares, as long as it has that coating on it, it helps keep the salt residue off.
To this day you couldn't tell my boat was in the Salt.
Golden rule is to heat shrink any connections for wiring. I still had to replace wiring after while tho.
I agree with Walt, but I do realize that if you get into a habit of being anal about taking care of things, it will definately help. However, salt crystals form in places you can't even see. When they dry, they expand and cause problems. No matter what, you are not going to get all the salt residue out of your risers/manifolds when your done. The flushPro that most people use, only fills up the risers at an idle level. That means you are not getting the salt out of the top of the risers (inside). After a while, that is why you have to replace them.