prop corrosion

[Freedom]

I pulled my boat this fall for winter storage. I found a thin line of rust on the edge of the prop blades. It's a folding prop so I sent it to PYI for some service it needed. The service manager there thinks this is from a sudden spike of electricity. The shaft zinc was like new & the prop zinc was in almost new condition. This is in fresh water, not salt water. The PYI manager said he rarely sees any corrosion in fresh water boats. A slow steady current leak should have eaten the zincs first, right?

The boat was pulled in 2008 and the prop was fine. So this happened in the April to October 2009 time period. The adjcent slips were empty until mid summer but both of those boats showed no signs of corrosion. I did take a 10 day trip and stopped at 4 marinas along the way.
No changes were made to the electrical system before this occured.

[capn chuck]

Freedom, I wonder what type of anodes you are using, zinc, magnesium, etc? Chuck

[Freedom]

Chuck

Not sure

[capn chuck]

I am sure Arild will jump in here at some point, but I do know that zincs in fresh water can form a coating which will actually stop them from doing their job. We usually install magnesium or aluminum anodes in fresh water. Did you actually find rust, your blades should be bronze, or was the metal a pink color? Chuck

[Freedom]

Sorry I can't recall the exact word PYI used to describe it (CRS). Yes it was not rust since the prop is bronze but it was rust color. I didn't think to take a picture, I'll ask PYI if they can.

Thanks

[Freedom]

Here is a picture PYI took for me