Anode & prop condition- Great Lakes

[kayakerChuck]

I've been around boats my entire life, but don't have much experience with inboards.

I'm near Detroit, and we are in the water 6 months/year. We bought our 1979 O'Day 30 three years ago, and the prop & shaft looked like new. It was kept in clean, fresh water. I don't know the composition of the previous anode. My current slip is in fresh water, but it's pretty "active" with combined sewer overflows and other yuck.

This is my magnesium anode after one season.


And, here's my prop:


Do these look "great", "OK", or "OMG"?

(Most of the other boats around me have cleaner looking props and anodes. i suspect most of the anode on the other boats are zinc.)

[Mirage35]

I'm in Kingston (Lake Ontario).

My shaft anode has never looked anywhere near that bad. I change it every two or three years just because, but probably don't need to.

My prop looks a bit like that but a little work with a scrubbing pad confirms that it's deposits, not corrosion. But yours looks worse.

That's the extent of my expertise - it looks to me like you have something going on that I don't.

[wrwakefield]

Originally Posted by kayakerChuck

…
(Most of the other boats around me have cleaner looking props and anodes. i suspect most of the anode on the other boats are zinc.)

Just a point of clarification: only magnesium or aluminum anodes [anodes are alloys] perform as anodes in fresh water. [Use one OR the other; not both. Aluminum also works well in salt water.]

Zinc alloy anodes will just crust up with a surface coating rendering them ineffective in fresh water.

We are in NNE Pacific [salt] waters but frequently anchor in areas with brackish waters [large fresh water discharges diluting the salt water; e.g., large rivers, glaciers, etc.] so we use aluminum alloy anodes with good success.

See boatzincs.com for one source of technical info on this topic.

I might try switching to aluminum anodes during your next haul-out to compare results. (It may not make any difference, but won’t cause issues either…)

FWIW

Cheers, Bill

[Tsuru]

Instead of guessing consider doing a corrosion survey with a reference anode. I used one like this but I’m sure there are others available. https://boatzincs.com/cre/
The reference anode along with a multimeter will tell you exactly where you stand.

[boatpoker]

Originally Posted by Mirage35

I'm in Kingston (Lake Ontario).

My shaft anode has never looked anywhere near that bad. I change it every two or three years just because, but probably don't need to.

My prop looks a bit like that but a little work with a scrubbing pad confirms that it's deposits, not corrosion. But yours looks worse.

That's the extent of my expertise - it looks to me like you have something going on that I don't.

If your anode is lasting 2-3 years ... it's not working. it's supposed to corrode.
I'd bet you have a zinc anode which simply does not corrode in fresh water to to the calcareous coating that forms on it.

http://www.pcmarinesurveys.com/Anode...0Corrosion.htm

[kayakerChuck]

My friendly, local, boat surveyor guy just bought another boat, which is now hanging in the hoist next to my boat. Good timing :-)

Joe asked me some questions about the bonding system, and says this looks as it should.