Not so pretty in pink...

Brought the boat to the yard today and left before they pulled it out of the water. Got a call from the diver who has an office at the yard and he said the props were on the "pink" side and might not be savable. I have a bad feelin' that they are churnin' up business and the props are not that bad. It's a ninety mile round trip to go look at the props and I am agin' it. I am goin' to wait and see what the yard says. Either way, I'm not buyin' new props. Could the yard refuse to "splash" the boat without new props?

Have them send you some pics. Easy enough to do with a cell phone. Don't think they can force you to buy new props. Not much fun though to have a trip ruined by throwing a blade, especially if you knew it was likely to happen.

Ted

Pink bronze is a well known phenomenon due to galvanic action selectively removing zinc (or aluminum) from the bronze alloy, known as "dezincification" (or dealumification in the case of Nibral). It is caused by insufficient zinc anode protection.

It can significantly reduce the strength of the bronze prop and makes it much more likely that hitting something in the water will break a blade or just throw a blade when under high speed.

Look at the prop. Is it a pink color all over. If so remove the prop and have a good prop shop look at it.

David

We were told something somewhat similar during a haulout a bunch of years ago. A prop shop (not the yard) said our props were "worn out" as evidenced by their sharp trailing edges and also that there were signs of electrolysis damage. They recommended we get new props.

We had the props reinstalled-- the yard manager felt they would be good for another season at least---- but also asked acqaintances and friends in the marine industry for their recommendation of the best prop shop in the Puget Sound area. They all independently gave us the same answer.

Talked to this shop at length, found out what kind of information and data they needed to determine the best new props for our boat, and then a few months later had the boat pulled and took the props to the shop.

They put the props on their test rig and came out and told us they were fundamentally fine but had been horribly set up by whoever did it last, which would have been before we bought the boat. We asked about the electrolysis and they said there are almost always some little dots of this on a prop and they saw nothing to be concerned about on ours.

So instead of buying new props for a couple thousand each the shop simply reworked ours for less than $500 each.

So you might want to get a second opinion on your props from a different and reputable prop shop.

I dwelt with this last fall. The boat I bought had sat in the water behind the PO's house. He was unable to maintain the boat and I believe let the zincs go for some time. We noted some of the problems during survey but after purchase, I had the boat hauled for some work and the extent became much clearer. The "excitement" of the discovery got the best of me and I believe I overreacted to the yards recommendations. Ended up replacing both struts, both main thru hulls and seacocks, both rudders (one was bent anyway). Props were fine. I also had a marine electrician investigate the cause and he determined that my bonding system had failed. Many of the wires had corroded. I replaced all using marine grade wire and terminals. Then after splashing, all items were retested by electrician at my slip.

After the work was done, I did some additional investigation. One of the struts was truly bad. Drilling in several locations it showed pink about a 1/8' deep and sounded a dull thud when struck with metal hammer. The other strut was truly just surface pink and sounded with a ring. It was going to have to be removed and realigned for the shaft anyway so I had decided to order a new one and replace it. I am keeping that as a spare now. The bent rudder was condemned and not able to be straightened. The other rudder was just pink on the surface and determined to be fully serviceable. The seacocks were both leaking and were not economically rebuildable per the yard. I ended up replacing a strut and rudder that I did not need to.

Lessons learned:
I don't think the my yard acted maliciously but when the surprises happen, I can't let the heat of the moment and the percieved pressure of the yard force me to do anything until I have time to investigate and satisfy myself.

Electrolysis did not effect all components equally. Each item needs to be investigated and a cause determined.

The Sicilian talked me into goin' down to the yard and lookin' for ourselves. Will take some pictures and post them.

Good to hear you're taking a first hand look. PM me if you need the name of a reputable prop shop in CA. This one is near Sacramento.

ancora said:

The Sicilian talked me into goin' down to the yard and lookin' for ourselves. Will take some pictures and post them.

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I expect you will not regret taking the time to check. Your boat is much younger than mine, yet mine is still on the original bronze prop.

Decent quality bronze props are not that easy to de-zincify. They would have to be very under-protected, something I doubt your boat would be. I'm amazed how long those bronze props last. Check out Marin's post again on that as well.
In my experience, they are more at risk of being worn down by the need to grind the barnacles off each haul out time. PropSpeed definitely lessens that risk, because the prop stays so clean, but have a look at this prop of mine, the original, and it's now 40 years old.

They cannot prevent you from splashing, but it may be a good idea to start researching new prop's, I was recently told the same thing, after checking the prop was in need of refurbishing, I bought and fitted a new one and now carry the refurbished one as a spare.
The yards reputation will soon be tarnished if they are having you on.

Ken's Marine Hardware in Gulfport Miss has a large offering of used props if you find yourself actually needing to replace them.


1983 Present 42 Sundeck
Twin Lehman 135's

Almost all props are Manganese Bronze. This is not a true bronze and may contain up to 35% zinc which puts it in the Brass class. Poor anode maintenance, lack of galvanic isolator or isolation transformer could easily cause the zinc in the manganese to act as an anode and leave the propeller. This is what causes the pink colour. Get someone you trust to look at the props. This is not something to take lightly. Losing a blade at 1000rpm can have devastating effects.

If you replace the props, take a look at Nibral, a few more bucks but not susceptible to electrolytic corrosion.

I've got an extra set of nibrals sitting in storage if you need them. 2" shaft 27x27 3 blade Michigans.


Via iPhone.

Went down to the yard and looked at the props. Pink all over but I rubbed a spot with emery cloth and found the bronze part. Gave the blades a tap with a ball peen hammer. The starboard prop blades all responded with a "ring", while the port prop blades resounded with a dull thud. Not too sure if that means anything but the props are Taiwanese so they may be made of different alloys. Gonna call a prop shop tomorrow for an estimate on "reconditioning." Here are the photos...

I'm no expert, .....
That's it. I'm no expert?


1983 Present 42 Sundeck
Twin Lehman 135's

Just have em re-zinked.









Prop shop time.

One looks fairly pink, but what do I know, I'm not an expert.

My surveyor said the same thing. Pink prop. Getting to the end of its life. Shipwright said it was fine. The boat is now in freshwater 9+ months a year. Maybe I'll take it to Osborne Propellors this spring at haulout. Frankly I'm not worried.


Jim
Sent from my iPad using Trawler Forum

I called Propellor Solutions in San Diego but they never called back Looks like we'll splash as is.

Do you have shaft zincs ahead of the strut? They go a long way in keeping the prop cathodic, that is, protected.

Put shaft zincs on if you can.

Hard to tell from photos, but they don't look too bad to me. At trawler speed props are not stressed much.

The one that does not ring- check prop nuts, could be loose. Not a bad idea to pull prop and check shaft, a crack in it can cause a dull ring.

I like the zinc bullets that mount to the prop nut, right close to the screws to do the most good.

I'm a believer in shaft brushes...have installed them on my last 3 liveaboards and the equalization of zinc depletion has evened out and become satisfactory and manageable for boats left in the water all year round.

psneeld said:

I'm a believer in shaft brushes...have installed them on my last 3 liveaboards and the equalization of zinc depletion has evened out and become satisfactory and manageable for boats left in the water all year round.

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We don't have one but thinking about it. Any suggestions or pictures?

There are commercial ones available...

I made mine out of a piece of bent, scrap aluminum with a one inch by one inch piece of old zinc that came off of an outboard (grabbed several for spares at the marina recycling bin). The zinc already had a bolt through the middle so I just added a jumper wire from that bolt to my bonding runs.

The aluminum arm is attached to a stringer with only one pivot screw but is left loose so the weight of the zinc keeps the arm on the shaft.

Sorry no pics..but there are nice copper/bronze ones available on the net ND plenty of pics if you google.

Mine is buried under the aft head sink so pics would be a pic but will if you like.

Our boat is fitted with the Ever-Guard system where everything is bonded to two large plate zincs on the transom and a reference zinc under the hull. Any additional zincs will negate the effect of the system. Don't believe it but we were told by the yard that once a zinc is out of the water it is no longer useable. Anyone else ever heard that? I'm talkin' salt water here.

ancora said:

I called Propellor Solutions in San Diego but they never called back Looks like we'll splash as is.

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I don't get this. Your yard identified a problem and you drove 90 miles and confirmed it might be a problem. You seek professional advice for a sound opinion. They fail to respond so you ignore the problem and splash the boat? What am I missing here?

ancora said:

..Don't believe it but we were told by the yard that once a zinc is out of the water it is no longer useable. Anyone else ever heard that? I'm talkin' salt water here.

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They sit awhile on shop shelves before they get sold and fitted.

Shaft brushes are good, but there are lots of opportunities for poor connections from shaft all the way back to transom zinc. Shaft zincs right in front of strut have a better chance of making a good connection.

Best is to have both.

OP photos did not seem to show any shaft zincs in view.

I still had the stainless arms left to our shaft "brushes". I took an electric forklift motor brush (same as a starter brush) and epoxied it to the arm. I drilled a hole in the arm, and used a small bolt to fasten the pigtail from the brush to the bonding wire. Has worked fine (I guess) for a couple of years. Will shoot a pic Sunday when I go to the boat.


1983 Present 42 Sundeck
Twin Lehman 135's

I am not about to pay lay days to the boat yard while I find a prop shop willin' to do the work.

Did you put shaft zincs on?

Greetings,
Mr. F. Did you use conductive epoxy? If not, have you checked the continuity between the "business end" of the brush and your grounding system?