I had the same problem on a Yanmar 2GM20
on my previous boat. It would chirp very faintly when running but I didn't have any oil
pressure or over heating
issues, all was normal. I know it worked normal when I sucked a ice bag up the intake and the engine
unfortunately, I could never source the problem so I just ignored it for 10 years until I sold the boat.
Sorry, not much help on solving the problem but it might ease your mind a little.