I use wd-40 and spray it over the engine after I give everything a rinse. It will displace the water and give a small amount of protection over all the metal surfaces. I use my Speedster an a regular basis so I don't look for long term protection. I go through a small can about every 3 outings. Pay attention to the jet pump area to add to protection to all internal parts in the pump. Works for Salt water or Fresh water.
Karl