There are some good advise and info in these posts, modern vs old. However, when we talk about a ‘salt water engine’ as an antique or classic, is one that was used in salt water and generally not taken care of. "To take care of" means flushing the engine every time used with fresh water so the water passages are cleaned. In a test tank you can use some soup to help clean the insides. Before you launch spray a light oil on everything, like WD-40, CRC or even a homemade brew of 1/4 WD-40 and 3/4 a non-detergent 30w oil in a used sprayer bottle like windex or the like; and then spray again after use. For must of us when we say a ‘salt water motor’, it probably has the water passages clogged with salt corrosion (and will not pump water) and is probably ugly on the outside as a tell tail. To buy is a gamble that Kenny Rogers will hold on. They can be repaired not easily, but consideration of time vs the rarity has to be considered. A classic I would pass on as there are more out there, a "square tank" depending on desire for it or rarity, I would consider. Hope this helps!
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