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Old 01-12-2021, 08:29   #1
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Best way to remove old bottom paint

So, I have 2 bow thruster props, 4 blade, 8" diameter, bronze (not sure which kind).

They were "accidentally" painted over with bottom paint about 5 or 6 years ago (an ablative paint, possibly Micron CSC) by an over-zealous yard guy who thought I wanted them painted.

I've tried some paint remover (Max Strip). I actually was able to remove about 2/3rds of it after soaking it overnight and then using a hand held wire brush. But still, only about 2/3rds.

Now what?

Do I go buy another bottle of paint stripper and keep going?

Or, can I get it sand blasted? There's a local place here which does stuff like this at very reasonable prices.

Or, should I put it in a vice and use a wire brush on a drill or angle-grinder?

Or.... is there some other way I am unaware of?

I don't think they need to be mirror polished or anything, but I would like to get them "clean" again.

Thanks in advance.
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Old 01-12-2021, 09:40   #2
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Re: Best way to remove old bottom paint

Try soda blasting over sand/glass or wire brushes that could damage the props. They sell small soda and sand blasting kits that work with lower cfm compressors for small jobs, so you could pick up a unit for yourself which comes in handy for other things as well.
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Old 01-12-2021, 10:08   #3
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Re: Best way to remove old bottom paint

One thing to be aware of with wire brushing, that I found out the hard way the first time I built an engine with aluminum heads, is that wire brushing can leave microscopic particles of the brush material in the surface of the material you are cleaning.

I think this is likely to be a problem where the brush is steel and the material you are cleaning is softer, e.g. steel, brass, possibly bronze.

The embedded steel particles will obviously corrode and damage the object you brushed.
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Old 01-12-2021, 10:13   #4
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Re: Best way to remove old bottom paint

A brass wire cup brush in a drill will take a lot of paint off a prop. As will a carefully used sander, using just the edge of the disc. With the sander, be careful not to also take off a bunch of metal, especially if it's a rotary sander instead of an orbital.



Honestly, my preferred method of stripping paint off a prop (unless the paint is really thick) is to wad up some paper towels, wrap a piece of sandpaper around it and go at it by hand. Basically, a sanding block that I can shape as needed.
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Old 01-12-2021, 11:32   #5
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Re: Best way to remove old bottom paint

I use a Dremel with "finishing abrasive brushes". They come in 3 colors of varying coarseness. My 9 inch prop eats 3 during the process but each year I end up with a magnificent bronze prop.

...

Before I then proceed to spray paint with rust oleum zinc, which is highly effective at preventing growth for my cruising area (middle Chesapeake) but does make it look way less pretty while it's on land. Oh well, the fish don't know the difference.
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Old 01-12-2021, 11:59   #6
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Re: Best way to remove old bottom paint

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Originally Posted by ArmySailor View Post
I use a Dremel with "finishing abrasive brushes". They come in 3 colors of varying coarseness. My 9 inch prop eats 3 during the process but each year I end up with a magnificent bronze prop.

...

Before I then proceed to spray paint with rust oleum zinc, which is highly effective at preventing growth for my cruising area (middle Chesapeake) but does make it look way less pretty while it's on land. Oh well, the fish don't know the difference.
Interesting - do you mean one of these maybe? I may try this.

https://www.amazon.com/Dremel-EZ474S...USW/ref=sr_1_4

If you use the rust-oleum, which is basically paint right, you sand it off each time you haul out and repeat this process?

Thanks!
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Old 01-12-2021, 12:16   #7
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Re: Best way to remove old bottom paint

To add. Those brushes are not metal.
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Old 01-12-2021, 15:45   #8
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Re: Best way to remove old bottom paint

Quote:
Originally Posted by flightlead404 View Post
...wire brushing can leave microscopic particles of the brush material in the surface of the material you are cleaning.

I think this is likely to be a problem where the brush is steel and the material you are cleaning is softer, e.g. steel, brass, possibly bronze.

The embedded steel particles will obviously corrode and damage the object you brushed.
I agree. I was going to use a brass cup brush - I think I may start out with that to get the paint off and then finish with the Dremel abrasive finishing tool which Armysailor recommended.
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Old 01-12-2021, 15:48   #9
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Re: Best way to remove old bottom paint

Quote:
Originally Posted by rslifkin View Post
A brass wire cup brush in a drill will take a lot of paint off a prop. As will a carefully used sander, using just the edge of the disc. With the sander, be careful not to also take off a bunch of metal, especially if it's a rotary sander instead of an orbital.

Honestly, my preferred method of stripping paint off a prop (unless the paint is really thick) is to wad up some paper towels, wrap a piece of sandpaper around it and go at it by hand. Basically, a sanding block that I can shape as needed.
Great feedback thanks. I was leaning towards the cup brush and a drill, since I have one. The whole paper towel/sandpaper trick sounds interesting though, I bet that could be handy in other situations as well. I think maybe with 40grit paper I could make some headway against the bottom paint, but the drill sounds faster and easier if I'm being honest.
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Old 01-12-2021, 15:50   #10
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Re: Best way to remove old bottom paint

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Try soda blasting over sand/glass or wire brushes that could damage the props. They sell small soda and sand blasting kits that work with lower cfm compressors for small jobs, so you could pick up a unit for yourself which comes in handy for other things as well.
I've heard of soda blasting. Unfortunately the shop I usually use doesn't do soda blasting and I've been unable to find another blasting shop locally which does soda on small scale projects like this.

If I had a house I would totally own a compressor and various pneumatic tools, but I live aboard and don't think I could convince the Admiral it was worthy enough.
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Old 02-12-2021, 03:47   #11
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Re: Best way to remove old bottom paint

So some owners do antifoul their props and others don't. Probably depends on various use and environment factors. It may pay to find out just why people make these decisions. Ask around friends with similar issues/circumstances. My own boat swings a 21 inch bronze prop and frankly I have no preferences, but my boat spends much time in a marina that has both salt and fresh water washing through. Have tried both polishing and various anti-foulings over the years.
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Old 02-12-2021, 05:27   #12
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Re: Best way to remove old bottom paint

Here is an alternative thought. If itís been a while since youíve had your props reconditioned send them out for reconditioning and they will come back clean and shiny and properly balanced. I just had mine done after 15 years and they look like brand new. Good luck
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Old 02-12-2021, 06:40   #13
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Re: Best way to remove old bottom paint

https://www.3m.com/3M/en_US/p/d/b40064937/

These are outstanding in this application. I use them every fall to remove the antifouling from my prop.
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Old 02-12-2021, 09:51   #14
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Re: Best way to remove old bottom paint

Why bother?
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Old 02-12-2021, 10:29   #15
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Re: Best way to remove old bottom paint

Try soaking Terry cloth cut in strips in paint remover. Wrap prop and let sit several hours. Baste the towling occassionally with more remover. Unless it is some sort of epoxy paint that should work.
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