The Gospel According to Nigel Calder

[Gary Wyngarden]

When it comes to boat maintenance, my guru is Nigel Calder. While reading up in Marine Diesel Engines on how to fix a minor leak in the anti-ciphoning vent in my raw water cooling line, I came across a couple of references to the importance of and need to periodically replace the sacrificial zincs in my heat exchanger. While I've replaced the zincs on my propeller shaft, I've not done this on the heat exchanger. What's more, I can't find any. What's even more, the owner's manual for the Yanmar 3gm 30F on my boat doesn't mention any zincs and the maintenance schedule in the owners manual doesn't mention replacing them (not surprising if they aren't there). Am I missing something here? Any help would be appreciated.

 

[Eric Lorgus]

Engine has zincs only if direct sea water cooled

Gary: I came across the same issue while perusing my Yanmar Service Manual, but then later realized the reference was solely for "direct sea water cooled" engines, i.e., those without heat exchangers, where the sea water itself passes through the coolant jacket of the engine.According to my Yanmar manual, the 1GM10(C), 2GM20(C), the 3GM30(C), and the 3HM35(C) all have anticorrosion zincs. The (F) series do not.

 

[Doug]

Another note...

I also found Nigel's strong mention of that concern important and began a search for our 2gm20f header tank zinc to no avail. I purchased the book to find the same thing Eric did. Still not wanting to give up, I called 3 separate dealers of Yanmar marine engines and asked for the tech expert. It turns out that not only did yanmar not feel it needed (by the way, the only marine diesel manufacturer that doesn't)but also nobody has retrofitted them with zincs for the fresh water cooled engine and in addition they have seen header tanks 10, 15 or more years old with no noted galvanic corrosion. I guess Yanmar knows best.Happy sailing.Doug