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Old 01-09-2017, 12:28 PM   #7
djmarchand's Avatar
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 4,888
Originally Posted by tadhana View Post
There is a good argument that Aluminum anodes are a better anode for most any (non aluminum) boat and drive system (non aluminum). We changed from zinc to aluminum 3 years as we go. We go from salt to fresh and back to salt several times per year. Most of our year we are in brackish water. But I don't think anyone is making aluminum pencil anodes for engines. Let me know if you find a source. Cummins has told me that zinc engine anodes are fine even if you are using aluminum hull anodes. My own recent history confirms this.
#$%&, you are right. I just assumed that boatzincs would have aluminum pencil engine anodes. I just checked. They have magnesium ones, but strictly for fresh water use, not both. No aluminum anodes.

So I guess you flush and hope that your zinc anodes are still good for the few hours you run in salt water.


When I write the article I will discuss the various commercial solutions for plumbing in a flushing system, but the home brewed system is by far the cheapest and works well.

smitty477 and others:

Cummins 6B and QSB engines have after coolers with a vertical bundle which lets condensate on the air side sit on the o-ring joint and corrode it out quickly. Yanmar engines have a horizontal bundle which lets condensate sit in the lower part of the shell so it is away from the o-ring joint for the most part. It does corrode though and after ten years in service my Yanmar 6LY was difficult to pull apart and had some light corrosion.

I am surprised that other after cooler designs don't use an o-ring or gasket at the water/air joint. I can't see how you could build them otherwise, but I have no personal experience other than Yanmar and Cummins.


I have been recommending an extended after cooler service interval if you flush with fresh water. I am not going to do that any more.

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