Removing salt residue

[PabloPicasso]

I want to touch up the paint of an inboard engine. There was a leak from a water gasket at the top of the engine and there is both some surface rust, and salt crystal residue. The engine is in situ beneath the cockpit but access is read able with the companionway steps removed.

So how best to remove the salt before preparing the surface for painting?

I can't use much water as the starter motor and other electrics are in the way and I really don't want to dismantle them. Suggestions please