Okay, I have avoided asking this here, because I thought I knew what to do. Well, I have read a dozen articles including all the ones from previous years on BABC, the often linked Boaters Ed Mercruiser thread, searched every forum out there, and I hear "Use zinc chromate primer", Don't use zinc chromate on an aluminum drive", "sand or grind entire drive to bare metal", "don't sand all the paint off, only the corrosion parts"
blah, blah, blah. So I have come back here to ask what you would do, have done, or will do concerning re-painting a Volvo Penta sterndrive.

I trust you guys for honest no BS answers, so please guide me through this.

Thanks in advance.

Make sure you guy silver/pray paint and as far as that I have no idea...that is my honest, non BS answer.

Take it from me, remove the least amount of paint possible. You will not get anything to stick like the factory finish and you'll be repainting the corroded areas every year from now on. I made the mistake of sanding the entire drive and now I have to paint it all every year and it sucks.
As far as the primer, I use whatever basic grey primer they sell at Walmart and it works great. It's the paint that I can't get to stick, no matter whether it's overpriced Mercruiser paint or Wal Mart paint. But the Mercruiser primer and Wal Mart primer seem to hold up pretty good.
Best of luck.

From what I have been told by a few dealers is that key to proper adhesion is a primer with zinc chromate. I also have to touch up some areas on my drive. This year I plan on using Interlux Primocon following the directions prepared below followed by a couple coats of Quick Silver Mercruiser paint.

http://www.yachtpaint.com/USA/boat_painting_guide/pdf/antifouling/outdrives.pdf

Zinc chromate primer. They use it on airplanes, and I used it on my Alpha. My problems were because I didn't prep the surface well enough, if I were to do it now, I'd have no problems.

Be sure to paint it black. Those silver outdrives just look silly.

What was it that Henry Ford said? "You can have your Model-T any color you want as long as it's black" or something like that.

I can't really hose it down in the storage facility, any ideas what to use to get all the sanding dust off before applying primer ?

I've got a spray bottle filled with water for when I wet sand. Then before I start to apply primer, I wipe it down with wax & grease remover.

Just used this method on 'vette parts and they came out better than I could have ever imagined.

And make sure you mask the surrounding areas real well.

Thanks F14, that's a good idea. Yep, I will be masking everything around it, as the boat is sandwiched amongst many other boats. I don't want any overspray on my boat or anybody else's. I thought I would blast it with an air compressor first, then wipe it down. The zinc chromate paint seems to just come in green or yellow, any color better than the other for a silver final coat? Also, I have heard you can spray clear over the silver final coat (per Wet Dogg's expert no BS advice)for extra protection. Necessary, or just fluff?

That advice will cost you...

Checks' in the mail........

Clear is obviously optional in this case. Its really up to you, and the look you're trying to achieve. You want the primer to be as contrasting as possible with the final color. This comes from the guy I know at the local auto parts store, that I've bought paint from. When the Corvette was painted two years ago, it was a black primer followed by the Competition Yellow.

You may find it necessary to wet sand the primer before color is applied. And when you're done sanding and inspecting the surface, always go by feel, not by sight. Your eyes can play a lot of tricks on you with surface preparation.

A good paint job is 90% prep work, and 10% actually spraying.

I'm sure the drive will come out great.

Where are the 10 other checks I am still waiting for

I spent them on outdrive paint. And a bottle on Bombay for when the job is done.

So green primer I guess? Yuck.

First time when the factory original paint started coming off, and after I finished it off with a little accidental sandblasting, I sanded the area to smooth the transition from old paint to new and went to the boaters store and picked up the closest color I could. No primer, just gunmetal colored outdrive paint, which was darker than original, and sprayed the areas that were bare, feathering into the original paint.

That came off within a few trips.

So, I went out and got the zinc chromate primer, and ordered the correct VP paint. Sanded the areas again, applied the primer, let it dry completely, roughed it up with a scotch bright pad, and applied the correct VP paint.

That lasted a couple of trips and started coming off.

So there is my no BS, but I think it is BS that I can't get the paint to stay on my drive!!

Good info CMJ. I have heard similar stories. And I am worried about the same thing. I know a few guys that just sanded their outdrive, and painted it with anti fouling bottom paint. It keeps the zebra mussels off, and barely needs a re-paint after 2 seasons in the water. I thought about doing it that way, but just did not feel like painting it in that evil color. I realistically don't expect this paint job to last 7 years like the original, but if I can get two seasons out of it, and keep the corrosion from getting too bad, I will be satisfied.

I suppose I should clarify my no BS statement. I meant no Black Sterndrive.

I had a similar experience. Paint started coming off lower section of outdrive from the fist day it was in the water. Dealer repainted once, looked like crap and the paint continued to flake off. Dealer repainted again, looked a little better but continued to come off. Ended up bringing it to an auto body shop. It now looks great and the paint looks as good as new after a complete season. Sorry to say I have no idea how it was prepped or painted.

Aluminum is tough to get anything to stick to but if it is prepped right and you use good paint it should last a long time.

I can tell you from personal experience,(I was just painting some aircraft parts at work today), that rattle can paints are usually too thin to do much good. They have to be super thin to come out of the can with just the aerosol pressure. To keep it from being too runny they make it dry super fast which prevents it from flowing around the tiny bumps in the primer. That means it lacks mechanical grip.

The industry standard for aluminum is to prep the surface with a medium/fine grit. This slight texture provides mechanical grip or "tooth". After brushing/vacuuming as much dust from the surface as possible wipe it down with a solvent that is compatible with the primer, often what is suggested for clean-up will work fine. This will remove any wax or grease that may contaminate the finish and cause fisheyes. Do not use water. An acid etch solution can be applied to etch the surface as well. Vinager will work. Then spray with Zinc chromate,(lovingly referred to as 'green death'), followed by a two part epoxy. Some primers want the top coat to be applied nearly immediately so that the two coats become one. Others want the primer to cure fully before top coat is applied.

You can rent an air assisted airless sprayer which is what Boeing uses, or a conventional air gun and compressor for not too much money. But with all the work and expense it might be simpler to take it to a body shop.

Hope this helps.

Read this about painting aluminum drives.

Also, if I recall, there is a nice section in the Volvo owners manual or maintenance manual about repainting a Volvo drive.

As mentioned earlier, I have read the B Ed link, and it is usually the first one posted here when outdrive painting is brought up. And like I said, it says not to use zinc chromate primer, and most other articles and dealers tell you to use it.
The original poster also states later, "If you are going to paint bottom paint on an aluminum hull, it needs an insulating layer or non copper paint usually one that contains a zinc derivative." If you use bottom paint, zinc is okay, but not okay if you use the paint and methods he describes on an aluminum outdrive.

So who do you believe ? A guy shows an outdrive that has a beautiful(expensive) paint job, with no follow up on how long it lasted, or a dealer who has painted these a certain way for years with good results?

Thanks for all the ideas and comments guys. I am less optimistic about a lasting finish now,not from what everyone has said, but just from the inconsistencies of methods and results. I will make an attempt at it, and no doubt learn something in the process

Well, I just add as a final thought, I have not used zinc chromate primer and the primer is the only thing that I can get to stick. My problem is the black paint not wanting to stick to the primer. Since you have a VP and it's already a little grey, maybe yours won't look so bad if the paint peels but the primer stays?!

Primer is yellow, if the gray peels off when it hits the water April 15th, it's gonna be one fugly lookin' sterndrive for 6 months.

I appreciate the input from everybody. Keep it coming.

VP actually do an aerosol can spray on antifoul paint in a grey that is quite similar to the normal paint. It seems to spray on quite well but the spray nozzle tends to partially block, giving the previously beautifully applied paint a quick spatter finish! The paint is unfortunately dissolved by the gear oil ( as I found out when I overfilled the drive once!). Works quite well as an antifoul as well but is quite expensive.

Here in the UK there is a Marine paint supplier called Blakes; they do a product called " Waterline", that is suitable for painting outdrives. That is available in "Volvo Grey", which is what I use now; thinned down with about 10% thinners, 2 coats plus an extra one in high wear area like the skeg, drive "bullet" etc. After last season, my drive had no barnacles and only a very slight covering of slime.

Update: Out drive is primed with Zinc Chromate primer. Volvo Gray paint arrived today. I should get that sprayed on tomorrow.
Just in time. 10 days until spring launch!

While I know zinc primer is used for aluminum aircraft, I have no idea whether it is suitable or not in a corrosion active marine environment.

I raised an eyebrow to the comment about zinc chromate on the B-Ed article. I am going to speculate here (ok - WAG); Its been my belief, from the corrosion book I have, that the zincs used for anodes have to be a certain alloy or they won't be effective, or maybe it was that they needed to be pure zinc, I cannot remember. I can look it up if need be, but the idea I got from the book is that unless specifically designed as a zinc anode with the correct metallurgy, it probably won't act like an anode. So I am not sure if I quite agree that zinc chromate is detrimental. But the bottom line is that I really don't know.

On the other hand, I know that zinc chromate is used in aircraft for unpainted areas, such as the insides. So if the zinc in the zinc chromate is indeed for corrosion protection (which I don't even know that for sure), it would then seem it would have to be an appropriate zinc formulation, and then it would be a bit like painting a zinc anode over the aluminum. Zinc is less noble than aluminum, so it becomes the anode. But again, I don't know if the zinc in zinc chromate is for that purpose or not. The only real thing I know about zinc chromate is that it is a funky color.

The main thing though is that the paint, whatever you use, is going to be the first line-of-defense against corrosion. Sure the sacrifical anodes will do their job, but its also essential that the paint sufficiently electrically insulate the aluminum.

When you are all done, are you thinking of changing to magnesium anodes?

I started using magnesium the last two years I had my Vista, and found that I had to replace the horseshoe anode each year, as it had significant eroding. That tells me it was protecting the drive.

Contrast that to the zincs I had on the engine - when I upgraded to magnesium, they were the originals on the boat - 4 or 5 years old, and only superficial erosion. That tells me that they were not protecting the drive as well. As a result, I did have some superficial corrosion, and if I still had the boat and those anodes, I'd be doing what you are doing.

I am not going to say that magnesium will completely cure the problem, but it has to help.

The first year I bought he magnesium anodes, I went to our favorite "sports center", and they had no idea what a magnesium anode was, so I had to order them on-line.

The next year, after discovering the anodes eroded as much as they did (I did not anticipate that so I didn't order any), I was able to buy them at the local dealer.

Either the dealer started carrying them, or maybe its because I finally talked to Joe - which to me was the only one in the parts dep't that knew his stuff.

By the way, if one were to bottom paint an aluminum hull or outdrive, instead of insulating this and that, as in the B Ed post, why not just use something like Interlux Trilux - which is designed for aluminum in the first place (I am not sure, but I don't think it has copper in it).

Pictures???