I recently used the Trilux 33 system on my running gear (shafts, struts, props, and rudders) and it seemed to work well. The system consisted of an etchant type primer, a base coat, and the top coat. I just followed the directions and the running gear's stayed clean (7 months on it) in our warm, South Fla water that grows barnacles in less than 2 weeks. I think the most important thing is to get your lower units very clean so the primer will bond well. And make sure you don't paint over your anodes.
50x15 Burns-Craft in South Fla
This was posted on another forum by a guy who does good work.
Painting Aluminum. It should be an oxymoron. But it happens. Especially aluminum out drives. I recently pulled my Mercruiser Bravo III. After 4 years of my paint job on it, not a single square inch of paint had eroded or peeled from the unit. Here is how I did it and some rules to remember when painting aluminum.
Number one. Aluminum will not take paint. Not bare aluminum, not etched aluminum? Surprised at "etched aluminum"? You see a lot of primers that say, "self etching". Well etching is the process of using acids or bases to remove aluminum oxide and other contaminants. Where do the contaminants and oxides go in a "self etching" paint? That is correct, they are contained in the paint job. How long and how durable is a paint job with "self etching" paint after all those contaminants are contained therein?
Number two. Alodine will adhere tenaciously to aluminum and paint tenaciously to alodine. So alodine is our "negotiator" to paint aluminum. It provides the intermediary between paint and aluminum.
Surface prep. A lot of options here. If the paint job is original Mercruiser it comes off very easy because Mercruiser has a poor process. You can sand it off for the most part. If you want, you can get some "aircraft stripper" available at most automotive paint stores or Aircraft Spruce. The main difference here is the amount of ammonia in the stripper. What is critical in this process is to place several plastic bags over the input shaft and bearings and the prop shaft and carrier bearings and hold them in place with tape. If you have a nearby facility that does plastic bead blast paint removal, like an aircraft paint shop, they can clean off your drive as well. Just make sure to cover the pitot tube entrance on your drive. DO NOT SODA BLAST. You will make the etching process a very difficult one. Get the drive as best you can down to bare metal. DO NOT USE STEEL BRUSHES, STEEL WOOL, STAINLESS STELL BRUSHES, etc anywhere, any time. Always use aluminum oxide sandpaper and if you want a "brush" use Scotchbrite pad.
Etching. I use AlumnaPrep 33 available at Aircraft Spruce. You dilute it 1 part to 3 parts water. A quart bottle is more than enough for one drive. Follow the instructions on the bottle. USE RUBBER GLOVES. Brush the solution on generously. If you see a spot repel the solution it may have grease on it. Degrease it with acetone or MEK and put on more Alumnaprep. Leave the Alumanprep on at least 3 minutes then flush with fresh water. Use a hose. Flush like crazy. Your drive should have a dull but bright look to it after etching. Allow drive to air dry.
Alodine. Again available at Aircraft Spruce. Do not dilute. A quart will do a drive. Brush it on your dried, etched drive. Again, if you areas that are aluminum that repels the alodine, you go to de-grease. Clean and re-etch. Then alodine. Do not flush the alodine, allow it to air dry on. Your drive should have a nice "golden" tint to the bare metal.
Paint. Here is where you have some choices. I personally prefer two part epoxy polyurethanes. They are extremely durable, flexible (hard paints crack), and give an easy and very shiny finish that remains that way. The only negative is, any corrosion occurring beneath the paint surface will not be visible. The paint may bubble, but the coating will remain intact. Make sure you have sanded and etched away all previous corrosion before painting. I use Southern Polyurethanes. The other negative to polyurethane is you want a very good respirator and face shield when you paint. You can get one a Home Depot. Do not get the disposable kind. Get a 3M 4000 or 5000. Do not allow this stuff to get in your lungs. It does not come out, ever. Make sure your mask seals tightly around your face. If you have a beard, shave it.
Priming. I use Southern Polyurethanes Epoxy Primer. For a Mercruiser use black. Follow the instructions for mixing the hardener with the paint, (It is one to one). I use a small eight-ounce touch up gun. It just about covers a drive. First spray a flash coat, and then come back with a wet coat. After this when the wet coat is highly tacky and not subject to running, come back again with a full second coat. If you feel rich and want to burn some paint put on a third.
Zinc-Chromate Primer. A lot of people swear by this stuff. It is very good coating on etched aluminum, but not under water! It contains zinc! Think about that for a moment? There is one place to use zinc-chromate. On your bearing carrier after repainting the drive.
Color Coat. I use Southern Polyurethanes Universal Black, 4000 series. Again just like the primer, activate it one to one. Spray a flash coat then a wet coat. I do two applications. You'll like this step because you'll be amazed at how bright and shiny your drive is.
Clear Coat. You can (optional) clear coat your drive with Southern Polyurethanes Clear 4000 series. Do it just like the color coat. You can buff it if you want. Alternatively you can put on clear anti-fouling. You have to be prepared that clear anti fouling will "degloss" your finish and after a few weeks in the water, it looks like your drive is "cloudy". Your underlying polyurethane finish is intact and is fine.
Refinishing. As I said, I recently removed my drive and the paint was intact, but I wanted to "clean her up". I removed the clear anti fouling with #60 sandpaper. I roughed up the polyurethane finish coat with #60. In the process, I broke through to bare metal in a couple of spots. No problem. Etch those spots with AlumnaPrep, then alodine them. I sprayed two coats of Epoxy Primer, two Coats of 4000 black, then two Coats of Clear.
1994 Sumerset 80'
Lake Lanier, Ga.
Thanks for the most complete step by step instruction on how to
paint an outdrive I have yet to see on the web, I don't want to
assume anything so excuse a couple of what may seem to you obvious
First is you have a section that starts with "paint" where you talk
about two part epoxy paint and then you go into the primer and
color coat paragraphs, I assume the paint paragraph is not a step
but your intro and comments about the type of paints as whole,
primer and color coat, stressing that the preference is two part
Secondly, The clear coat step, I am not clear on whether the whole
clear coat step is optional or if clear coat is a must but the
option is Southern Polyurethanes Clear 4000 series vs clear anti
Did you also paint where the anodes go or did you have to mask them
to allow the anodes to do their job by being in direct contact with