How many zincs ?

Ready to get the spring short list ready. We have only owned this boat for about six months. So on the list is a zinc change. I have 6V92 Detroits. Does anybody have any idea how many zincs are on these engines ? I have only located two so far, one just before the main engine cooler and one in the trans/fuel cooler unit. Im thinking there should be more. I have seen what may be a zinc in the bottom of the exhaust manifolds but the are very small plugs that look more like a drain plug. Anyone have any ideas ?

here is a start and these guys are GREAT !!! https://www.boatzincs.com/detroitdiesel.html