Dakka the best thing you can do is flush your engine with fresh water as soon as practically possible after you've put it back on the trailer. You only really need to run in for a few minutes after it reaches operating temperature(So the thermostats are open)

 I use it and like it a lot. When I first bought my boat my starboard engine wouldn't pee on the muffs without raising the revs for a few seconds. Then it would start but it was more of a dribble. I started using SaltAway and since then the engine pees freely without having to raise the revs. Of course, since then I've done a service for my own piece of mind and found the impeller was in great condition although I replaced it anyway. I'm thinking there must have been a blockage somewhere else in the cooling system but whatever it was it has since been flushed through and the engine pisses freely now. I think it's good stuff.

A second reason I'm sold on it is that recently I was running the engine on the muffs with fresh water when I heard a low pitched drumming noise coming from the leg on the Port engine. I immediately thought the worse and began worrying that a bearing was on it's way out in the leg. I switched on the SaltAway to flush the engine and immediately the noise disappeared. I believe the noise was just the impeller making a drumming noise in the carrier due to a lack of lubrication in the fresh water. The SaltAway acts as a lubricant within the water pump carrier. It must be said that the noise wasn't bad, I've just got a keen ear for things like that but was glad when it immediately disappeared when I switched the SaltAway on.