Went to change my engine zinc in year 3+ of ownership. It unscrewed and the brass cap came off. When I tried to put in the replacement, it would not go. I felt around with a finger, then screwdriver, and there's something up there - I'm thinking the partially corroded zincs from prior years (the zinc part screws into the brass hex nut cap, and I'm guessing it corrodes itself out of the cap socket). I can't get the new one in, and I can't get the cap to screw fully on. I noted a bolt on the side of the heat exchanger, and I thought I could remove that bolt and pull off the side and see what's blocking things. The bolt came out easily, but the side did not - at which point I decided to put the bolt back, and Ask The Experts, rather than forcing things.
I ran the engine successfully after putting things back together and noted no leaks and proper exhaust water, but I'd feel better with a new zinc and a cap screwed on fully. See attached photos. Engine is a universal diesel M25-XPA with 695 hours. I have the original manual, and one is online here: http://www.westerbeke.com/OnlineManu...erator_man.pdf
At start and end of Year 1 this replacement went fine, though I noticed some shards of prior zincs. At the end of year 1 I installed a galvanic isolator, and made a note wondering if the zincs would last longer. My notes show the zinc was down ~1/2 at end of year 2. So the questions are:
1. how should I investigate this further without damaging things?
2. should I expect that my zinc from prior years to last much longer?
3. what risk am I taking just leaving things alone for another X months, and trying again?
Thanks for your support.