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#392492 - 03/27/08 05:11 PM
Re: Painting a Volvo DP
[Re: Wet Doggg]
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Admiral
Registered: 10/02/06
Posts: 2134
Loc: Oldsmar FL
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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!!
_________________________
Take care, Chris 06 Monterey 248 LS
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#392601 - 03/28/08 05:37 AM
Re: Painting a Volvo DP
[Re: trooplewis]
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Scallywag
Admiral
Registered: 06/21/04
Posts: 7877
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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
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#395445 - 04/08/08 01:02 AM
Re: Painting a Volvo DP
[Re: Capn Morgan]
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Nautical Alchemy
Admiral
Registered: 01/14/03
Posts: 11541
Loc: Battle Creek/Grand Haven, MI
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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).
_________________________
"Yesterday's Dreams"1995 Carver 325 Aft Cabin  Posts are amateur opinion only. You assume all responsibility for any action you take as a result of reading my posts.
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#395758 - 04/09/08 05:27 AM
Re: Painting a Volvo DP
[Re: Al]
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Scallywag
Admiral
Registered: 06/21/04
Posts: 7877
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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).
As I mentioned when I started the post, too many different recommendations out there, and I hoped I could get real world experience here. It seems there are no clear cut "best" way or paint to use. Some work better than others, some don't. Several Volvo tech's and mechanics recommended the zinc chromate primer for the Volvo outdrive I have. So I went with that. Any Interlux product was triple the cost of what I got. I am cheap, so did not go that route. Not worried about the zincs , as mine are still acceptable in their current condition. After 7 seasons in the water, there was not much corrosion. I feel that says they are doing an adequate job. I will hopefully be able to get into the storage facility tonite to paint the top coat of Volvo-Penta Gray, give it another coat Saturday and be done with this project for now. Pictures ???? Most likely not. My work will be adequate, but not good enough to display to the world. Billy, if you really want to see the finished paint job, I can PM a pic to you. Okay maybe too much information, but this is as good a place as any to air it out. I am not mechanically inclined, I do very little repair work at home or on the boat. Just something I never really took a liking to. I do not enjoy tinkering, or seeing if I can make something homeade myself, rather than buy it. I am the farthest away from a "project guy" you will ever meet. I decided to tackle this task by myself to see if I can actually do it . For the record, I have not added one single option to this boat,have never drilled a hole anywhere in the boat. The extent of adding an improvement to the boat was placing a flat screen TV in the cabin, not mounted, just resting on a shelf in the bow. That's it. I have replaced plug wires, cap,batteries,engine and outdrive oil,and other fluids as needed. Painted the bottom twice, rubbed out and waxed the hull each year, and routine cleaning of the vinyl and upholstery. I allow Cheetos to be consumed anywhere on my boat, at any time. I am a believer in "If it ain't broke, don't fix it" . It has worked for me for 14 years of boating, but this time, I am taking a chance that I can actually "fix" something that really wasn't broke, but needed some attention. We will see. Non Anal Cap'n. 
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