[metalmassfab]

If the marine engine was used in saltwater, stay away from it. Most all marines engines use whatever body of water the boat as its coolant. A block that has had saltwater running through it is bad news. Not much you can do with one, boil it out, bake it, freeze it, the rust will keep happening. Aluminum manifolds, radiators, etc. will feel the effects much sooner as well. My father has been a commercial fisherman (among other things) for over 30 years. We've seen countless times when someone 'scores' on a marine engine, and bad things soon follow. The higher nickel content, thick walls and such are because of the corrosive environment the engines live in. A little more nickel = a little slower to rust, a little thicker walls = they can rust a little longer before death. Electrolysis is bad news...