Paint the prop?

[mikebikeboy]

1980 Cape Dory 27, I beleive the prop is bronze. Can't tell but maybe previous owner painted it, but not sure. It's dirty. Should I paint it? If so how should I clean it without damaging it?

[SVHarmonie]

You clean it by using a wire brush. NOT a steel one! In fresh water, there isn't much need to paint it. If you do, be sure to use paint made for props, or underwater metals in general.

[Captn_Black]

Ni-Cad Bronze is literally the best material available for seawater. If it weren't so expensive you could build unpainted boats from it. So no.
The copper content also means it is about as effective as hard antifouling naturally. That doesn't mean you don't have to take a wire brush to it occasionally.

[a64pilot]

Most paint the prop, the argument is what to paint it with.
You can do just about anything to a bronze prop and not hurt it, most will sand off the old paint. But scraping and I assume chemical stripping is fine to, I often hear of 80 grit to give a good surface for paint.
I have in the past put bottom paint on mine with good results until the paint comes off which it will. Many use zinc rich primer, and there is a Petit zinc prop paint that is supposedly identical to the zinc rich primer, just several times more expensive, I have used the Petit product and wasn’t impressed.
I’ve not found anything really worth bothering with, I just scrape my prop leaving it bare metal.
If I was in cold water, I’n be much more likely to try prop speed, and there are very mixed reviews on it, apparently you must follow directions exactly or it won’t work.

[Captn_Black]

Originally Posted by a64pilot

Most paint the prop, the argument is what to paint it with.
You can do just about anything to a bronze prop and not hurt it, most will sand off the old paint. But scraping and I assume chemical stripping is fine to, I often hear of 80 grit to give a good surface for paint.
I have in the past put bottom paint on mine with good results until the paint comes off which it will. Many use zinc rich primer, and there is a Petit zinc prop paint that is supposedly identical to the zinc rich primer, just several times more expensive, I have used the Petit product and wasn’t impressed.
I’ve not found anything really worth bothering with, I just scrape my prop leaving it bare metal.
If I was in cold water, I’n be much more likely to try prop speed, and there are very mixed reviews on it, apparently you must follow directions exactly or it won’t work.

I assume you mean ablative paint? I don't see the point of using hard anti fouling on it, and I would disagree with "most", unless we are talking aluminium outboard props.

[mikebikeboy]

Wow thanks for all the responses! I'm in fresh water, and when I look closely at the prop I see signs of the previous blue that the hull was painted, which is bottomkote ablative paint.

[Captn_Black]

Originally Posted by mikebikeboy

Wow thanks for all the responses! I'm in fresh water, and when I look closely at the prop I see signs of the previous blue that the hull was painted, which is bottomkote ablative paint.

No worries, don't be afraid to use a steel brush, NiCad Bronze is tough sh*t, unlike regular bronze.

[a64pilot]

Originally Posted by Captn_Black

I assume you mean ablative paint? I don't see the point of using hard anti fouling on it, and I would disagree with "most", unless we are talking aluminium outboard props.

I’ve had three kinds of paint on my prop, hard antifoul which worked the best, ablative which works until it comes off and the Petit product which I don’t think does much.
I don’t clean a prop with a wire brush and don’t know any that do, it won’t remove barnacles, but then I’m in salt water, sometimes brackish, but never fresh.
Walk the boatyard, most props will have evidence of some kind of paint on them, but as I said I don’t think it does much, if anything it may make the barnacles easier to remove as the bond between the prop and the paint may be weaker than the bond between the barnacle and paint.
I use one of these things, the curve will usually fit the shaft and maybe some sections of the prop.
https://www.lowes.com/pd/Blue-Hawk-P...-tool/50094752
Maybe a wire brush is for fresh water?

On edit, what is NiCad Bronze?

[Captn_Black]

Yea, I use a pallet knife for barnacles. I've never sailed in fresh water with my own ship either. I guess the question of "most" is anecdotal in both our cases, but if you ask a salesman whether you should use something instead of nothing then the answer is to be expected. I cleaned a lot of hulls on my first boat, before internet working was really a thing, mostly in Bahamas, and didn't see many painted props. But then what other sailors do isn't necessarily based on empirical evidence.

Edit - I'm quoting mostly from Bruce Robert's books on the other matters, and his opinions seem based in science.

[Frankly]

I have been painting props in Florida waters for over 50 years. Organo tin was the the best (for the prop not the environment). Hard epoxy based antifouling will last about a year with pretty good results, ablative is gone in a matter of days. Getting ready to put the last coat of Pettit Trinidad on my new Autoprop this afternoon and install it tomorrow. Rense and repeat next year.

To get paint to stick to clean bronze seriously rough with 80 grit paper (sometimes I get out the sand blaster), clean with paper towels and acetone multiple times (typically at least 3), you will reach a point where the feel of the paper towel on the prop feels different (now it is clean), use rubber gloves and prime with epoxy. After the epoxy is partially cured paint first coat of bottom paint. I usually put on three. Sometimes with a little scraping I go two years but that is about it. Typically get 3 to 4 years out of a bottom job with hard bottom paints (Pettit or Seahawk).


Frankly

[Cheechako]

I scrape with a spatula and or wire brush. Paint the prop. The paint will come off the blade edges for maybe 1/2" but that's ok. Paint doesn't stop barnacles from attaching though but helps some. Kills them eventually. But if you dont keep moving you'll have to dive down and scrape eventually. At least paint the hub portion.