powder coating outdrive

[farmboy]

Re: powder coating outdrive

The original owner of my Sea Ray was a party hound I think. He had the boat pulled to a local lake where it spent the next three years dockside. The boat was run up and down the lake 50 hours or so. The guy sold it to me because, "it was running sluggish". The point being, after three years in fresh water, the zincs needed changing due to moderate erosion but the drive metal was still very nice. After pressure washing a ton of growth off the hull and drive, the "sluggish" boat ran as good as new. While a good paint job helps, it is my opinion that cathodic protection is more important than the coating for protecting the drive. There is a lot of material out there (google marine cathodic protection) but a specific system for your particular application needs to be used as stray current can destroy not only your drive, but also the drives on craft moored near you. VP surely has offered CP solutions for their drives.

 

[j_cizzo]

Re: powder coating outdrive

J Cizzo, A pink drive...now that would be different! The aluminum drive case all by itself is fairly corrosion resistant in the atmosphere. You are talking about protecting the drive while its submerged most of the time? Galvanic, not paint protection is the paramount concern I would think. A well applied quality coating will help insulate the metal and thus contribute to less corrosion risk but the coating alone will not be enough to protect the metal. I am not qualified to comment on anything but basic cathodic protection, but I do know that galvanic current has to be directed away from the drive or you will lose metal pronto. One of the neccesary ingredients for corrosion is electrolyte (water). The more mineral content (salt) in the water, the more efficient the electrolyte. It was mentioned above that all zinc anodes be in top shape and I agree as those sacrificial zincs are designed to be the first things to go. Whatever you do, do not coat the drive metal where the zincs mate up. Anything that insulates current from traveling between the drive metal and the zinc will render the cathodic protection they furnish useless. I have read about drives that were electrically bonded to provide additional protection but I am not familiar enough to comment. Dockside, dedicated cathodic protection for marine applications maybe an option that someone here might know more about.

I know about the impressed current setups (mercathode and vp's version as well) but the problem is that it's moored, so eventually the batteries will drain. If there's one advantage though, since it's out in the harbor the stray currents aren't too bad. i do replace the zincs every season and they don't dissolve too quickly.

regarding the pink drive, ok, ok, i was just trying to prove a point... i can't afford to go replacing an outdrive right now. maybe next season, but not now...


so back to the drive, maaan i'd love to put one of those composite drives on this thing.... anywho, so i was looking at the thing last night and it's got some barnicles on it and is kinda funky, it ultimately should be blasted and repainted from the ground up. so what should i be using? i'd assume that paint technology has come a long way since the drive was built and that i can do a better job then the factory.

soo what? clean, etch-prime, imron?

 

[gene8084]

Re: powder coating outdrive

Isoo what? clean, etch-prime, imron?

Found this a while back on Mercstuff.com how tos?

Painting an OutdriveThis can be a simple project, with so-so results, or complex with great results or something in between. I have a lot of technical knowledge about coating metals, but won't bore you with all that. Here is what I would do:

1. Prepare the chipped spots with a small tool (I like a small sanding wheel on a Dremel tool). Make sure you clean any pits to the bottom of their depth. You may need to use a Dremel tip grinder to do this... but failure to clean pits all the way down will ensure their return. Feather to the existing coating surface. Leave the exposed metal surfaces "sandpaper rough" to aid paint adhesion.

2. Use a paint dulling compound (available at paint stores, etc) on all remaining painted surfaces. Use fine steel wool to rub this in and very finely scratch the surfaces. Once finished, use a very dilute ammonia solution to wash the entire unit, then rinse thoroughly with water and wipe dry with clean cotton rags.

3. Use "metal prep" (like an iron phosphate or zinc phosphate solution... zinc is best if you can find it) on any bare metal spots. Metal prep is an acid, so be careful. Dob it on exposed metal spots (only) and allow it to air dry very slowly to build its crystalline structure (microscopic) on the surface. Do not wash.

4. Once everything is clean and dry, spray the entire unit with a good quality zinc-rich primer. I would do two coats on two successive days, if possible.

5. Top coat with a high quality enamel or better yet, Dupont Imron polyurethane enamel. I would do two coats of this as well.

That's it. The toughest decision is how much stuff to take apart to get at the components. I'll leave that to your judgment. The most important thing is this: paint only sticks well to very clean, very dull surfaces. Good luck!

Cheers
Curt crussell@termcorp.com

Thanks Curt,

Mercstuff

 

[farmboy]

Re: powder coating outdrive

Gene8084,
I tend to agree with this KISS method of painting a drive unit. The only comment I would suggest is to use one coating manufacturer's products and talk to that manufacturer about their recommendation for the application. If your using Imron, then the wash primer and any zinc-rich primers used should be compatible as a total coating system.

 

[jasonpauthement]

Re: powder coating outdrive

I have just finished powder coating one of my two Volvo 290 DPA out drives . As stated, the rubber seals in the out drive will need to be removed form the units. My father was a Volvo dealer and I am lucky enough to have all the tools from Volvo to tear down the unit. After tearing down the units, I made some plates out of metal to cove all the opening to the inside of the unit and cut a gasket then bolted the plate on to the three housing for the unit. I did not make a plate for the top of the transmission, I used the actually cover for it ( the one with the oil dip stick). Don't forget to remove the fork as well. If you are doing all the work yourself, use some tie raps to keep the shims with the proper bearings. I would also take pictures of every thing to make sure that you put it back together the same way it came apart.

Before the actually powder coating, if the paint on the unit is chalky and flaky, I would have to blasted with a medium that will remove the paint but will not penetrate and stick in the metal of the out drive, Walnut shells would be a good choice. After the blasting make sure to wash the parts well and clean with a solvent that will not leave a residue.
The paint that Volvo used is very hard and tough to remove. But what you are looks for is a very clean part.

After blasting and cleaning, I heated the parts to about 350 degrees before I started to do the powder coating. I did this to make sure that I was getting a good coating on the parts. I applied 3 coats, baked and then applied three more coats and baked once more. This also filled in the small pitting that I had in the out drive.

I did not take picture while I was doing it but I can take picture of the unit that I have not cleaned, and compare it to the unit that I did powder coat. I have not put the unit together yet, I am still waiting on a couple seals and bushings.

It took me about 1 1/2 days to do the unit, most of the time was in the cleaning and disassembly. I have also started to powder coat one of the engines (chevy 350).

Doing the same thing with paint and primer would have taken me 4 to 5 days. Between the sanding and the sand blasting and letting the primers cure to the bare metal. Aluminum can be tricky to paint when it is bare and paints and primers do not stick to it well with out taking the time to make sure it is prepared properly.

As far heating the metal up in an oven, You are not apply enough heat to the alter it. I have done some heat treating back in my Navy days, But that is done over 1000 degrees in a furnace, for an long time. Depending on the heat treating process that you want to do. 350 to 400 degrees at 20 minutes will not hurt the outdrives. It is very possible o do at home if you have the tools to tear down the out drive. Funny how you ask a question and you get tons of reply's and no one answers your question.

 

[thumpar]

Re: powder coating outdrive

You just replied to a 7 year old thread. The red bar at the bottom is there for a reason.

 

[Fun Times]

Re: powder coating outdrive

Funny how you ask a question and you get tons of reply's and no one answers your question.

Hi there jasonpauthement, welcome to iboats!

I'd like to thank you for taking the time to respond in detail of how to go about powder coating stern drives, the effort is very much appreciated. While some members may know about a subject others may not know all the small details and if they do, they may not have had the time to spend writing out a summary about it back in 2007. iboats is and always has been a very busy forum thus making it difficult to find then respond to all the questions that continuously come up daily though we all try our best to answer them in our spare time.

Because iboats if such a busy boating forum, our hosts would prefer to keep most technical questions that are over 90 days old stay down in the archives even if you have really good responses to add like done here. The theory goes that we would like to try our best to help the with the latest questions due to there usually is only a short window of opportunity to help the newest member because most members from the past do not return to their old questions if they even come back at all. Take this OP for an example, he has not been back online since August 25th, 2010 @ 12:27 PM and he is not subscribe to any thread subscriptions that would send him an instant email advising him someone posted to his old thread. Hopefully he has everything all squared away by now.

Not trying to be negative here, just letting you know the help is appreciated and it would be even more helpful if you would stay on board with us and post to current threads.

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