What are the strands made of ? copper?
Or are the scratch marks?
What is the silver material on the back side, lead? Silver ?
Brady
The electromagnet was made from a transformer. That was just the pic I found first.
Shell type transformer electromagnet.. Laminated steel sheets on the outside (that stacked look in the picture) and the bulge in the material is copper wiring (windings). The winding bulge in the middle probably had a divider material between them at one point. This one looks pretty toasted maybe it was in a fire or hit by lightning. This one is a little big but could have come out of an old school amplifier.
Hope this helps.
My first thought is sure these items could have been used in a boat motors especially vintage/homemade types, however, it's more likely it was used in some electric device on the mainland such as an amp, bipolar dc motor, things typically found in a garage that guys would tinker with stuff.
You mentioned you found other material around this item that gave the indication it was all incinerated. What were those other items by chance? If this was all part of a burn pit etc, someone could have just chucked it in by itself or was a smaller part of a bigger item that was burned.