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Deterring corrosion on aluminum alloys (Bravo III outdrive)

April 15, 2010

Hi, Just bought a boat with a Bravo III outdrive. I read many message boards about the corrosion issues that Mercuiser has had with earlier models of this outdrive, primarily 1998 thru 2003. The outdrive itself is aluminum. The propeller is stainless steel.
I understand why dissimilar metals can cause corrosion, specifically here. But I would like to know what process is best for priming and would be best suited for this application in the outdrive as-well-as what method of cleaning the corrosion is most effective.
I read one article that zinc chromate primer (which so many mechanics use) is NOT best suited and that it can cause or allow corrosion.
Someone else suggested a process of: Cleaning process - using Alumiprep 33 [on eBay or Amazon], then Alodine [on eBay or Amazon]. Painting - Two coats of: Epoxy Primer, Polyurethane Universal black, & then Clear coat it.
This boat will be used in fresh & salt water.

Thanks,

Dale Hill
The serious D-I-Y'er - Tupelo, Mississippi

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April 21, 2010

Hi, Dale. Your second proposal sounds good to me. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey