While the answer to this question may seem simple, there are a few factors that can play into how much scrap is produced from a boat rust. The size of the boat, the type of rust, and how much surface area is affected by the rust can all contribute to the amount of scrap that is produced.
In general, however, it is estimated that a typical boatrust will produce between 1-2 pounds of scrap. This means that if you have a large boat with significant rust damage, you could be looking at upwards of 100 pounds of scrap! Of course, this also depends on how you go about removing the rust and whether or not you plan on recycling it.