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Old 11-04-2017, 13:34   #1
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New Gori propeller corroded (pictures)

Hello!

Five months ago, I just pulled the trigger on a folding propeller, a 2 blades Gori. I bought the dimensions both Gori website and the dealer recomended. After 3 months, I realized I had lost the shaft anode and left 2 months to replace.
I thought "what can happen in only 2 months?" Well, You will see what can happen in the pictures attached.
This is corrosion? Cavitation? Stray current?
The previous prop stayed 20 years in place and was intact.
Gori website states that "cavitation may occur" on two blades propellers. But chating at my yacht club, many owners of folding propellers (2 or 3 blades) have this same problem (not so fast).
Have you had this type of corrosion on your Gori?
Thanks
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Old 11-04-2017, 14:31   #2
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Re: New Gori propeller corroded (pictures)

Looks like electrolysis to me:



That fluid, organic blob shape is a dead giveaway.
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Old 11-04-2017, 14:51   #3
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Re: New Gori propeller corroded (pictures)

So fast
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Old 11-04-2017, 17:00   #4
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Re: New Gori propeller corroded (pictures)

What size and pitch? I have one I'd sell 16.5 x 11 on the hub. Blades are 12 pitch basically new only kept as spares in case needed.
Hub is a bit pitted, but not as much as yours.
PM me if interested.

Steve
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Old 11-04-2017, 17:19   #5
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Re: New Gori propeller corroded (pictures)

Quote:
Originally Posted by carlo de leo View Post
So fast


If you or one of your neighbors has a D.C. Current leak.....yes, so fast.
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Old 11-04-2017, 18:05   #6
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Re: New Gori propeller corroded (pictures)

Quote:
Originally Posted by carlo de leo View Post
Hello!

Five months ago, I just pulled the trigger on a folding propeller, a 2 blades Gori. I bought the dimensions both Gori website and the dealer recomended. After 3 months, I realized I had lost the shaft anode and left 2 months to replace.
I thought "what can happen in only 2 months?" Well, You will see what can happen in the pictures attached.
This is corrosion? Cavitation? Stray current?
The previous prop stayed 20 years in place and was intact.
Gori website states that "cavitation may occur" on two blades propellers. But chating at my yacht club, many owners of folding propellers (2 or 3 blades) have this same problem (not so fast).
Have you had this type of corrosion on your Gori?
Thanks
Stray current electrolysis for sure. If you had lost an anode absolutely this could happen in such a short time, particularly in a marina. I had this on my Gori when I got the boat because the anodes were worn down and needed replacing. Once replaced (regularly) it never got worse. The problem is that depending on how bad this is your prop can get out of balance causing vibration. Hopefully it isn't that bad!
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Old 11-04-2017, 18:06   #7
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Re: New Gori propeller corroded (pictures)

If you are using shore power and do not have a galvanic isolator your zincs may be wasting more quickly than if you were by yourself. I think feathering/folding propellers may also be more susceptible just because of how they are constructed. A standard prop is one homogenous part fitted tightly to the shaft and benefits from a good connection to the shaft protective anode (zinc). A folding prop is a bunch of parts relatively loosely attached so connections to the protective anode are not as certain. A fish type clip on zinc attached to the prop shaft and hung overboard might help along with a galvanic isolator.
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Old 11-04-2017, 19:41   #8
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Re: New Gori propeller corroded (pictures)

Your zincs clearly need to be checked and probably replaced, (more) frequently. better to sacrifice them than a prop. Any new neighbors or have you changed locations?
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Old 12-04-2017, 03:22   #9
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Re: New Gori propeller corroded (pictures)

" I think feathering/folding propellers may also be more susceptible just because of how they are constructed. A standard prop is one homogenous part fitted tightly to the shaft and benefits from a good connection to the shaft protective anode (zinc). A folding prop is a bunch of parts relatively loosely attached so connections to the protective anode are not as certain.[/QUOTE]
As BGLAD said,
Yes, that is one thing I thought about the folding property. The eletrical connection from blades to the hub and shaft can be poor
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Old 12-04-2017, 04:40   #10
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Re: New Gori propeller corroded (pictures)

Good thing is your prop is basically fine, you caught it early. Definitely check the zincs frequently, particularly if you've moved to a new slip/marina and are staying for a period. Does not take much to eat up a zinc if your neighbor has a problem.
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Old 12-04-2017, 05:15   #11
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Re: New Gori propeller corroded (pictures)

Quote:
Originally Posted by buzzstar View Post
Your zincs clearly need to be checked and probably replaced, (more) frequently. better to sacrifice them than a prop. Any new neighbors or have you changed locations?
Yes, I've been for a month or so in another marina. There was a 74 feet motor boat beside me...
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Old 12-04-2017, 05:19   #12
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Re: New Gori propeller corroded (pictures)

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Originally Posted by Suijin View Post
Good thing is your prop is basically fine, you caught it early. Definitely check the zincs frequently, particularly if you've moved to a new slip/marina and are staying for a period. Does not take much to eat up a zinc if your neighbor has a problem.
Thanks, I think that's the case. I'm back to my original slip now and I'll haul out this year again, so will be able to check again.
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Old 12-04-2017, 19:57   #13
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Re: New Gori propeller corroded (pictures)

This was an uproar at the marina I was in in 1975 when a French yacht with, they said, reverse polarity and an electricity leak got a transient slip. As I recall they said 11 boats lost their props in about a week due to electrolysis. I was too far away for damage, but I remember angry folks out for blood between my slip and the parking lot.
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Old 13-04-2017, 03:35   #14
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Re: New Gori propeller corroded (pictures)

Looks a lot like a stay current problem. The zinc disappearing so fast was your first clue. The pink spots your second.

I recommend you have someone check out your vessel and systems with a silver half cell.
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Old 13-04-2017, 03:51   #15
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Re: New Gori propeller corroded (pictures)

I've posted this before but it's worth it again for this thread.

This is a sail drive what was the victim of stray current. And this is off a cat and the other was just as bad. It took approximately 10 days for this to happen. Stray current off victim boat itself:

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