Really?? No zincs
Scary stuff, my 5411 is saltwater cooled, no exchanger, and by rights should be a pile of rust with 4000 hrs. But not so. It is good and reliable. ( personally I think the hours meter has bee left running at the dock to rack that many hours).
Why would anyone make a marine diesel without zincs in the block? As long as nothing is broken I won't add an exchanger yet.