Engine anodes

[Triskele]

My boat is in fresh water. Have read where anodes for fresh water should be either magnesium or aluminum. Zinc for saltwater. I'm a little confused as to whether this rule applies to all anodes, boat and engiune, or only to boat. I am changing my engine pencil anodes and not sure whether I should be using aluminum or zinc. If aluminum, can someone recommend where to buy aluminum. Everywhere I look online seems to only sell zinc pencil anodes.

 

[MikeP]

Not an answer to your question, but FWIW:

At the end of last season when I was adding my usual two Zn guppies for winterizing I was at the local hardware store that carries them and, for the first time, they had AL guppies as well as the usual Zn guppies on the same shelves. I had never seen AL guppies before and, further, I thought they had just accidentally mixed them. But I went to a marine shop that had the same - some Zn, some AL in the same section, mixed together.

The shop owner said they had started carrying AL and was hoping to "phase out" Zn.

I have no clue about Zn vs AL effectiveness though I see on the scale that although AL is higher than ZN, it is still below any of the metals we are trying to protect so it SEEMS that it should work. I decided to buy one of each to see how they reacted over the winter. I'll check them on Monday when we arrive back on the boat. Seems like I read somewhere that there is a general industry nudge toward using AL instead of Zn in any type of water but I might be remembering that incorrectly...

 

[SEVEN]

I know for a fact that West Marine carries the Aluminum. They have a chart in each store identifying where to use them. If you have one of their catalogs it should be in there as well. I'm in fresh water and have switched to Aluminum.

 

[Walter P]

What are the advantages/disadvantages between alum and zinc? Longevity, effectiveness, price etc.

Walt

 

[MikeP]

I ran across this article that seems to indicate that AL is better in every way than zinc for salt/brackish water, especially for brackish. Also saying that neither is suitable for fresh water. But I have done no further research so there could easily be conflicting articles...you know how the internet is! It could be a marketing paper disguised as "information."

http://www.cruisingworld.com/how/zinc-and-aluminum-sacrificial-anodes

 

[SEVEN]

Funny my yard says the opposite. I was depending on them for the right answer. Typical. Fortunately I have the boat checked every 6 months.

 

[SEVEN]

Found this on line.