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Old 05-12-2018, 15:17   #1
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Feathered Prop Question

Looking to buy a sailboat to cruise the South Pacific later next year. Came across one that looks good, but am not sure about the feathered prop. Can someone tell me what caused this damage? It's bronze, so I can't see it being barnacles. And if it is electrolysis, should I be looking for other damage?

What about the strut?
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Old 05-12-2018, 19:04   #2
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Re: Feathered Prop Question

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Looking to buy a sailboat to cruise the South Pacific later next year. Came across one that looks good, but am not sure about the feathered prop. Can someone tell me what caused this damage? It's bronze, so I can't see it being barnacles. And if it is electrolysis, should I be looking for other damage?

What about the strut?
That is a max-prop, great propeller. But the damage looks like corrosion. Strut looks bad too. Hot marina or lack of maintenance of the zincs for a long time. Need to look at other metal bits on the boat to see if this corrosion (probably electrical galvanic corrosion) has affected other systems. Is water heater okay? Check it's zinc and element, also engine zincs (if any), thru-hull? Might need to pull the sea-cocks to inspect the thru-hull tail for corrosion damage.

Do you know any history for the boat?
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Old 05-12-2018, 19:15   #3
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Re: Feathered Prop Question

Looks like the Zinc is missing off of the end of the propeller. Eaten away and then attacked propeller and strut maybe? I would definitely proceed with caution.
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Old 05-12-2018, 19:43   #4
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Re: Feathered Prop Question

In addition to the above, you should have the holes closed by a welding shop, both on the blades and the strut. You must weigh the blades and get them identical, and even preferably dynamically balanced. You have to check for electrical leakage, otherwise you will be back here soon.
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Old 05-12-2018, 20:36   #5
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Re: Feathered Prop Question

Thanks SeaTechSystems and ontherocks83.

The broker said what was left of the zinc was removed, and the prop was stripped and painted. He also said the owner bought her 3 years ago but has never actually sailed her. He's is in the Navy. He said he was going to get out when he bought her, but they made him an offer he had a tough time refusing. It has been on the hard ever since.

It has a few deck leaks showing up in the ceiling from leaky hatches, and it needs new sails, but overall, a very good deal. Even the standing rigging is all swageless mechanical fittings, and the SS is in excellent condition. While the boat is dirty from sitting for 3 years, it has been plugged in the entire time.

No issue with replacing the prop, but is a strut like this common, or does it have to be made? Moreover, does it need replacing, or can I take it off and have it welded?

I already know the rudder is full of water, but I can rebuild it in my shop. The rudder post and skeg are solid with no shake.

I ran my moisture meter all over the hull, and the only spot I can find with any water intrusion is a 2" x 2" area top right of the genset exhaust thru-hull. Otherwise, she's tight, and the thru-hulls below the waterline all look good. I also metered the areas around the chain plates and there is no water intrusion into the DiviniCell deck core.

Now, the motor and genset turn over, so they should start. If there is anything left of the pencil zincs, should I be concerned beyond that? The aqua lift muffler is pretty rusty, but have no issue replacing it.

I will definitely heed your advice about checking everything that has saltwater in it, including all the zincs. And when I splash it, I will also run tests on the March pumps, the engine and genset, AC and the watermaker. If everything works, I should be okay.

Except for the corrosion issues, I am confident I can make the boat good again. I actually thought about forgoing the survey until I fix things I know insurance will have an issue with, but reading your comments, now I'm not sure. This will be my 5th saltwater boat, so I'm no rookie. I've just never seen that kind of corrosion.

I'm heading back to do a second look on Friday. I'll let you know what I find.
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Old 05-12-2018, 20:40   #6
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Re: Feathered Prop Question

Thanks sy_gilana. That answers one of my questions. There is a lot of beef still in the strut, so welding it works.

As to the prop, I'll just replace it and keep the other one as a backup.

Leakage. Not sure I can test for that until I splash it, but even then.... Guess I have some reading to do.
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Old 06-12-2018, 07:39   #7
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Re: Feathered Prop Question

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Originally Posted by CptCrunchie View Post
Thanks SeaTechSystems and ontherocks83.

The broker said what was left of the zinc was removed, and the prop was stripped and painted. He also said the owner bought her 3 years ago but has never actually sailed her. He's is in the Navy. He said he was going to get out when he bought her, but they made him an offer he had a tough time refusing. It has been on the hard ever since.

It has a few deck leaks showing up in the ceiling from leaky hatches, and it needs new sails, but overall, a very good deal. Even the standing rigging is all swageless mechanical fittings, and the SS is in excellent condition. While the boat is dirty from sitting for 3 years, it has been plugged in the entire time.

No issue with replacing the prop, but is a strut like this common, or does it have to be made? Moreover, does it need replacing, or can I take it off and have it welded?

I already know the rudder is full of water, but I can rebuild it in my shop. The rudder post and skeg are solid with no shake.

I ran my moisture meter all over the hull, and the only spot I can find with any water intrusion is a 2" x 2" area top right of the genset exhaust thru-hull. Otherwise, she's tight, and the thru-hulls below the waterline all look good. I also metered the areas around the chain plates and there is no water intrusion into the DiviniCell deck core.

Now, the motor and genset turn over, so they should start. If there is anything left of the pencil zincs, should I be concerned beyond that? The aqua lift muffler is pretty rusty, but have no issue replacing it.

I will definitely heed your advice about checking everything that has saltwater in it, including all the zincs. And when I splash it, I will also run tests on the March pumps, the engine and genset, AC and the watermaker. If everything works, I should be okay.

Except for the corrosion issues, I am confident I can make the boat good again. I actually thought about forgoing the survey until I fix things I know insurance will have an issue with, but reading your comments, now I'm not sure. This will be my 5th saltwater boat, so I'm no rookie. I've just never seen that kind of corrosion.

I'm heading back to do a second look on Friday. I'll let you know what I find.
Another thing, if you are in Washington.. PYI (who distributes the Max-Prop) is in Lynnwood, WA. You can content them and Jerome there rebuilds the props. You could send him the photo and get a high level quote. He may have some advice on the corrosion as well.

I have had my 21" 3-blade Max-Prop rebuilt a few times by PYI due to log strikes in BC (always BC, never WA or AK, funny enough). Anyway, rebuild is typically ALOT cheaper than a new prop.
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Old 06-12-2018, 08:41   #8
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Re: Feathered Prop Question

I am Certified Corrosion Analyst.

That is stray current corrosion.
99.99% of the time that stray current is coming from the vessel itself.

I'd bet that the prop and strut are manganese bronze which is roughly 35-38% zinc. To call this bronze is actually a misnomer as is metallurgical circles the high zinc content places it squarely in the "brass" class.

You cannot repair that by welding. Corrosion to that extent is deep within and throughout the metal. In fact the corrosion will be much more on the inside than what you can see on the outside. To demonstrate this I have attached an X-ray of a single pinprick size hole on a stainless steel shaft. The shaft photo clearly shows it was much worse under the surface.

You need a qualified electrician to track down the issue.

PS. No qualified person will use the term "electrolysis" so if he uses that term, find someone else.
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Old 06-12-2018, 09:01   #9
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Re: Feathered Prop Question

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I am Certified Corrosion Analyst.

That is stray current corrosion.
99.99% of the time that stray current is coming from the vessel itself.

I'd bet that the prop and strut are manganese bronze which is roughly 35-38% zinc. To call this bronze is actually a misnomer as is metallurgical circles the high zinc content places it squarely in the "brass" class.

You cannot repair that by welding. Corrosion to that extent is deep within and throughout the metal. In fact the corrosion will be much more on the inside than what you can see on the outside. To demonstrate this I have attached an X-ray of a single pinprick size hole on a stainless steel shaft. The shaft photo clearly shows it was much worse under the surface.

You need a qualified electrician to track down the issue.

PS. No qualified person will use the term "electrolysis" so if he uses that term, find someone else.
I believe the max-prop is Nickel-Aluminum Bronze, but I am not positive.
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Old 06-12-2018, 10:42   #10
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Re: Feathered Prop Question

Just got off the phone with Jerome of PYI (MP Service). He said, from photos, the prop can be repaired. They don't sell the 22" anymore, but he has the blades and the (something) to rebuild it if it needs it.

He quoted some rough numbers: $4600 new. Just new blades is $1600, with internals is around $2200. Welding it up is around $1500.

I played with the blades and the inner workings are very tight with no slop at all.

I sent off a photo of the strut to my local SS welder to see what he thinks. He repairs commercial vessels and is actually building a 70' all aluminum and SS sailboat in his yard. Charlie knows a lot about corrosion.

Now I need to check out all the other bits that have suffered neglect. Tomorrow is going to be a long day.
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Old 06-12-2018, 10:57   #11
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Re: Feathered Prop Question

*makes note of the term 'electrolysis'* Thanks.
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Old 06-12-2018, 12:39   #12
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Re: Feathered Prop Question

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I believe the max-prop is Nickel-Aluminum Bronze, but I am not positive.
If it is, the stray current is even more serious.
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Old 12-12-2018, 09:33   #13
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Re: Feathered Prop Question

+1 on PYI. Rebuilt my max-prop for a great savings. Just send them the entire unit and they will tell you your options.
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Old 12-12-2018, 09:41   #14
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Re: Feathered Prop Question

Something not quite right with that strut too, looks like someone welded a cutlass bearing on to the the strut. Not the end of the world but would plan on replacing the strut with a new bronze one.

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Old 13-12-2018, 19:27   #15
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Re: Feathered Prop Question

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Something not quite right with that strut too, looks like someone welded a cutlass bearing on to the the strut. Not the end of the world but would plan on replacing the strut with a new bronze one.



Pete


Youre right- thats why it looks weird. Id be worried if stupid shortcuts like that were done by builder or PO as what else will you find.
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