In article ,
Shortwave Sportfishing wrote:

On Mon, 28 Aug 2006 05:30:51 GMT, Eddie
wrote:

I have twin Merc cruisers outdrives on a 277XL Commodore Regal. The
mechanic wants $585 to sandblast, prime and paint.

That's not bad for New England.

Sandblasting aluminum seems to be a radically stupid idea. Pressure
washing removes whatever junk and loose paint just as well, but doesn't
damage the protective aluminum oxide film.

In article ,
Eddie wrote:

On Mon, 28 Aug 2006 22:36:23 -0400, Huss Mohrens
wrote:

In article ,
Shortwave Sportfishing wrote:

On Mon, 28 Aug 2006 05:30:51 GMT, Eddie
wrote:

I have twin Merc cruisers outdrives on a 277XL Commodore Regal. The
mechanic wants $585 to sandblast, prime and paint.

That's not bad for New England.

Sandblasting aluminum seems to be a radically stupid idea. Pressure
washing removes whatever junk and loose paint just as well, but doesn't
damage the protective aluminum oxide film.
Huss, are the outdrives made out of aluminum?

That's why the metal gets whitish rather than rusty.

I will install new
props, so not worried about that. You sound like maybe sandblasting
may not be the way to go. He did pressure wash the entire boat,
including the outdrives before painting the hull. But I notice the
outdrives still have a whiteish rough texture. I want the drives to
be smooth for painting. How else can I get a smooth finish?

The white stuff (hydrated aluminum oxides) must be removed, otherwise
your primer won't last. The easiest way is washing it off with an acidic
washing solution. Can't really recommend any "best" washing solution,
but the label should either warn that the product may damage glass or
explicitly state that it contains hydrofluoric acid. As an example, the
one at http://www.redarrowmfg.com/products/aluminumbright.htm looks good
to me.

When the white stuff is gone, you'll see how the metal surface really
looks like. Chances are, it doesn't need any further smoothing (other
than priming). The key is to remove ALL the white stuff, then wash the
surface with a lot of water, then blow off the water with compressed air
before drying.

If the surface is very rough after acidic cleaning, it may be blasted -
but not with sand. Soda is a much better idea, because it's not nearly
as abrasive as sand and the residues can be washed off after blasting. I
would rinse the surface with a lot of water after soda blasting, and
then with a gallon of 1% acetic acid just to make sure there is no
alkaline residue on the metal (soda is alkaline, none of it should
remain under the primer).