Volvo Penta 290DP Anodes - Zinc or Aluminium

[MartynJS]

OK. So I have always fitted Zinc anodes since I have been involved in boats. The DP leg has two: one block anode on the transom shield and the ring anode in front of the props. I noticed this year that most suppliers are offering aluminium anodes and that fewer zinc anodes seem to be available. The boat is kept in Weymouth, in the back water where it came become a little brackish, although it is tidal. I bit the bullet, this year, and went for the aluminium anodes on the basis of technical papers found on the web. So has anyone else made the jump to aluminium anodes and, if so, what conclusions have you drawn about their effectiveness?

 

[spannerman]

Mercruiser/Mercury have gone over entirely to aluminium for saltwater use, if your zinc anodes previously got a white coating on them thats a sign that they are in water that is more fresh than salt, and the coating then renders them useless in saltwater. So you should be fine with those anodes, just check that they are dissolving gradually, the worst thing is an anode that appears to last forever, as its not sacrificial which means other parts of your boat are now acting as anodes.

 

[Chris_d]

I have used them instead of Mag for freshwater use and they seem much better, not getting limed up and becoming ineffective like Mag, I have two DP290's.
Having used them for the last 6 years or so with the occasional Saltwater holiday of a month or so I would certainly reccomend them for mixed usage.

 

[tico]

Yup
I keep ours in brackish water and Zinc tends to grow a hard white scale which decreases the anodes effectiveness.
Changed to Aluminium anodes a few years ago , they work much better.

 

[MartynJS]

All very interesting replies. This year, the zinc anodes showed very little wear and I put that down to the amount of rain during the winter. The Ring anode usually looks like a lace curtain when it comes off after a year in the water. This year there was only one hole in it. I would not say that there was any white deposit but definitely some concretion. Several other people in the mariner made similar comments about their anodes this year. The props are still there, so I guess that the zinc must have done its job. Thanks for the replies.