Looking through the manual and I cannot seem to find this. The only thing I've come across that looks like it is a spring for the hinges on the front two storage compartments. But like I said I found this spring laying in the engine compartment.
No I have not. Looking through diagrams for this boat all I can find is one part that looks like that spring, and it's a hinge spring for the two flip up storage compartments. I cannot find anything else on this boat that uses that spring. No idea where it came from. The hinges for the engine bay trunk do not use that spring, only those storage compartments. Very strange.
Looks similar to springs on the seat position latches. It appears to be stainless, so it was expected to be wet. Can't say how it got to where you found it.
I went out to take a look at mine and it certainly looks like the one you are holding. I bet Tim may be right. Is one of your seats missing it's spring?