Here is a great write-up (targeted for Mercruiser): [url]http://www.mercstuff.com/painting.htm
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I re-painted my Mercruiser outdrive last year. I had pretty good results with a shorter process (for a 30+ year old drive that I didn't want to fully take apart). Here was my process:
1. Degrease
2. Remove areas of corrosion with Dremel and sander (I had quite a bit)
3. Scuff entire surface with sandpaper
4. Clean again
5. Clean with IPA. Mask transom, any attached anodes, hydraulic lines, fasteners, etc.
6. Prime any bare aluminum (I used this:
https://www.amazon.com/gp/product/B002984MU0/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
7. 2 coats of paint. I used this:
https://www.amazon.com/gp/product/B000B68V90/ref=oh_aui_search_detailpage?ie=UTF8&psc=1If my drive and boat were newer, I would probably have bit the bullet and gone with a more intensive process. This spring I did have to do some touch-up work on some areas that wore off (Primarily the Skeg). Personally I don't mind hitting a few spots each spring when I do my normal drive maintenance.
I failed to take a good before picture- but here is my drive with primer and completed:


_________________
-Andrew

1984 Four Winns 225 Sundowner
5.0L Mercruiser, Alpha 1