Anode Question

[bluemoose]

So, my new prop takes up a lot more room on the shaft than my old one, and I would like to put a line cutter up where the anode would normally go... Can I get by in fresh water with an Aluminum washer or two back at the retaining nut? This is assuming that it comes out every 6 months and I replace the washers every spring... Thoughts? Thanks!

[sestina]

Mount a hull anode wired in to the bits you want to protect. Lasts much longer than the puny shaft ones. You pays your money...

[foggysail]

Originally Posted by sestina

Mount a hull anode wired in to the bits you want to protect. Lasts much longer than the puny shaft ones. You pays your money...

I don't fully understand your suggestion.

The purpose of shaft anodes is to overcome the electrical resistance a transmission presents. I did away with shaft anodes some years ago but to do so I designed and made my own shaft brushes that ride on on the shafts inside the boat to provide bonding. Brushes are now cheap! Had I found them earlier I would have purchased them rather that make my own.

Further I recommend aluminum anodes in salt water over zincs because their electron capacity is over twice that of zinc and they are less expensive. I only use 1 diver's plate anode which works well as verified by my frequent measurements with a silver-silver chloride half cell.

[model 10]

foggysail; Could you elaborate on this aluminum anode idea? Why does everyone use Zink?

[foggysail]

Originally Posted by Guy

foggysail; Could you elaborate on this aluminum anode idea? Why does everyone use Zink?

Sure! Before I start, aluminum IMHO is the best kept secret for anodes. But an aluminum anode is more than just a chunk of aluminum. It should be made to the Navy's MilSpec Mil-A-24799. I have used them for years and only one at that on my 40' Silverton. Mine attaches to the stern....in the water of course...and is sufficient to provide all the protection needed from galvanic corrosion.

Everything you need to know is described in detail at

Anode FAQs
and
http://www.performancemetals.com/ima...m%20Anodes.pdf

And best of all, aluminum anodes not only will last longer, they cost about 1/2 that of zinc. The 1st attached URL gives so many more details on anodes, I recommend you go there to read the benefits.

Most guys who use zincs on shafts know from experience that they never seem to last long. There is also a poor electrical bond between the the zinc and the shaft. I HIGHLY RECOMMEND using shaft brushes to bond the shaft/prop to your boat's bonding. I have not looked for the commercial brushes although some have said they purchased a pair for under $100.

My first experiment with my brushes used bronze plates taht I silver soldered to brass bars that rested on the SS shafts. The bars/plates were made common with my boats bonding. That experiment was a failure. One short trip out almost destroyed the bronze that rested on the shafts. I had bronze dust all over the place. I solved that by using oilite (sintered bronze bearings) pieces that I bolted to the brass bars.

Foggy

[fstbttms]

Originally Posted by Guy

foggysail; Could you elaborate on this aluminum anode idea? Why does everyone use Zink?

Not everyone does use zinc. Aluminum anodes are becoming more popular and are being required by more and more boat builders.

[HoppySailor]

Magnesium anodes should be used in fresh water.

[foggysail]

Originally Posted by fstbttms

Not everyone does use zinc. Aluminum anodes are becoming more popular and are being required by more and more boat builders.

Well about time! However, if one did a survey here in Cruisers, my guess is 95+% will show zinc usage. Where I store and where I have a slip, I do not know of anybody else beside me who use aluminum. Might even be worth doing that survey.