Salt water really causes problems where dissimilar metals make contact (stainless bolts in aluminum). Whenever you do any maintenance to your ski, I recommend using an anti-sieze compound on the bolt threads (unless Loctite is used). I also recommend a total coating of Sea Doo Lube on the engine and jet pump after use.
Another good item to install in your ski, is an inline strainer. All you have to do is cut the water intake line (the black line that goes from the jet pump to the exhaust) and install using stainless hose clamps. These can be bought at West Marine or any other similar store. This strainer will catch any sand or seaweed before it reaches your cooling pasages.
If you have any other suggestions, e-mail me.