[mad_machine]

I would add to Rich's synopsis and solution to add that most sailboat diesels are not run long enough. To get all the condensation and such from the dry stack, the engine needs to get nice and hot and stay that way for a while. If you are not running it like that (and diesels tend to run cold at idle) all you are doing is adding moisture to the stack that is getting into the microfractures and forming more rust