Rinsing a stored engine with fresh water is probably a good idea. In fact BEOWULF is plumbed to allow us to do this. However, in all of our years of cruising we’ve never done it, so I’m not sure it is really necessary. One thing to keep in mind is that if the engine’s waterpump is used to suck in the water you are OK. But if you force it in under pressure, you have to be extremely careful not to get in any excess which would back flow through engine’s valves (since the engine is not operating and there is no exhaust pressure to force it out. Regards–Steve