Re: Freshwater PWC in Saltwater???
Okay. I think that you got the fact that you're going to have to flush it and wash it very well after you're done. I'd do it daily.
Now lets talk about your trailer. Is yours galvanized steel or aluminum? If so, no worries. Just rinse/wash it well.
If it's painted steel, then that's another story. Especially if it's a round tube or boxed steel tube trailer where you won't be able to rinse the saltwater out of the tubing.
Years ago when I bought my 1994 Yamaha WaveRaider brand new, it was a freshwater ski and it came on a painted, boxed steel tube trailer. When I move to Florida, I used the ski in saltwater and tried to rinse that trailer as well as I could. There was no way that I could rinse out the tubing and the trailer started rusting from the inside out.
If you had a freshwater pond or lake that you could back the trailer into after the saltwater, that may clean out the tubing good enough.
Here are couple of pics of what my trailer looked like the day I got rid of it:
