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Prop spots and discoloration

Old 01-14-2019, 12:58 PM
  #41  
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Kinda looks like a Yamaha Painted Stainless propeller that someone sanded down to make it shiny.
It does not appear like it was polished out after sanding, so its going to rust much quicker with the rough surface.
When I first saw it, I was thinking electrolysis, but as mentioned above, the anodes look fine.
And I don't know if those props have a different grade of stainless or not.

Maybe Parker Yacht, or Tom W Clark know if the painted stainless Yamaha is different grade then a regular stainless like a Saltwater Series or something.
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Old 01-14-2019, 02:34 PM
  #42  
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Originally Posted by ChrigelKarrer View Post
I don't think that this is a bad batch of Yamaha propellers as Yamaha uses high quality materials for their outboards and propellers.
Ummm, I'll just leave this one alone.

Originally Posted by InCogKneeToe View Post
They look like they were once Black SS Yamaha Props, polished off to look Shiny. Looking at the Rakes, and Exhaust Flutes, and No Exhaust Vent Holes or Names stamped in them.

Sub Stainless is most likely why Yamaha painted their SS Props in the first place.
This is an interesting thought.
Originally Posted by ken2 View Post
Kinda looks like a Yamaha Painted Stainless propeller that someone sanded down to make it shiny.
It does not appear like it was polished out after sanding, so its going to rust much quicker with the rough surface.
When I first saw it, I was thinking electrolysis, but as mentioned above, the anodes look fine.
And I don't know if those props have a different grade of stainless or not.

Maybe Parker Yacht, or Tom W Clark know if the painted stainless Yamaha is different grade then a regular stainless like a Saltwater Series or something.
I believe that the painted Yamaha stainless props were indeed a different metal than the polished ones. They definitely rusted in a different manner, but It could have been just the lack of polishing, but I'm pretty sure it was a different metal.
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Old 01-14-2019, 03:20 PM
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Just wanted to thank all that have helped try to solve this.
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Old 01-14-2019, 05:57 PM
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If I'm following along correctly, you stated 10 hours of use in between the 2 photos. Kinda hard to tell for sure but I opened the images on my PC and zoomed in real close.

It appears there is visible erosion of the anodes, especially starboard motors leading edge of torque adjust fin.

In the areas I boat, one would never see any change with the naked eye in 10 hours of run time. I would suspect you have a ground problem or something causing this, since you say you don't leave it in water near other vessels.

You state you have 3 batteries and also that you turn off each engines switch, which leads me to ask.......is there a battery ground cable connecting the negative terminals of all 3 batteries together?
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Last edited by Grunts N Grits; 01-14-2019 at 08:54 PM.
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Old 01-14-2019, 06:04 PM
  #45  
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Spray them with oshpo and rinse after 5 minutes
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Old 01-14-2019, 06:29 PM
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Originally Posted by Kiwi Mike View Post
Spray them with oshpo and rinse after 5 minutes
oshpo?
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Old 01-14-2019, 06:49 PM
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Originally Posted by pstephens46 View Post


oshpo?
Yes, that's the new naval jelly that's all natural, including the lint.
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Old 01-14-2019, 07:02 PM
  #48  
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Originally Posted by whorrall View Post
Hey not to derail the thread here but I've heard this about nonmagnetic stainless steel before, and i don't understand. The other day i was playing with my big rare earth magnet and noticed that stainless bolts stick to it, but not as well as regular bolts. Ferrous = iron containing, right? And steel is any alloy that contains iron, correct? So any stainless steel will stick to a magnet right? Or no?
I do this for a living so excuse me if I get long winded

Iron (Fe) is elemental and right at 70% of the composition of any 300 series stainless and is the mother of all ferromagnetic materials, so to speak. Some 150ish years ago we learned that the addition of a small amount of carbon increased it's properties multi-fold and we called this new wonder metal steel. Add 1.25% to 12% chrome and a kiss of molybdenum and now you have what everyone calls chrome moly - great for motorcycle frames, gun barrels etc. Add a little more chrome and ~10% nickel and you have a 300 stainless but let the mix slip a little and you have the OP's props.

Yeah those are painted Yam props - I would treat them to a 100 mile run to clean the freckles off and then prep and shoot some rattle can clear on them...is no great answer.
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Old 01-14-2019, 07:42 PM
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Lower grade material used in painted props. Might have been something you run thru in the water. Lots of bad stuff floating around in the water.

300 series SS are non heat treatable and more corrosion resistance with 303 being the easiest to cut and machine and 316 being the best for saltwater use. Non Magnetic and non rusting for most part.
400 series can be hardened. Most common in SS guns and high grade knifes. Magnetic and will rust.
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Old 01-14-2019, 08:45 PM
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Take the boat to a sandbar. Problem solved.
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Old 01-14-2019, 09:45 PM
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Are you using bleach to clean the boat ?, are you on a well or city water ? if a well maybe there's a lot of iron in the water. Just a thought.
I agree they look like "previously" painted props.
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Old 01-15-2019, 07:52 AM
  #52  
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Here is another angle from May 2018 As Grunts N Grits pointed out (good catch) The newer pic defiantly looks eaten away.


Jan 2019 Unfortunately I am away from the boat for possibly another 3 months. If this is electrolysis (which I have never had any first hand experience with) I don't know what to do at this point to minimize more damage. As I said all power is disconnected at the lift and no external AC cords running to the boat. I have both battery disconnects in the off position, and I can't check the battery grounds until I go back down. Also the only thing I can think of that would bypass the battery disconnects would be one of the bilge pump that is wired directly most likely.


Last edited by mikeloew; 01-15-2019 at 08:19 AM.
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Old 01-15-2019, 08:17 AM
  #53  
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I definitely see some growth or deposits on them. I would get them cleaned up real good and monitor closely. Also, that zinc in the second photo does look more eaten up.
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Old 01-15-2019, 08:34 AM
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Originally Posted by mikeloew View Post
Here is another angle from May 2018 As Grunts N Grits pointed out (good catch) The newer pic defiantly looks eaten away.


Jan 2019 Unfortunately I am away from the boat for possibly another 3 months. If this is electrolysis (which I have never had any first hand experience with) I don't know what to do at this point to minimize more damage. As I said all power is disconnected at the lift and no external AC cords running to the boat. I have both battery disconnects in the off position, and I can't check the battery grounds until I go back down.
Been dealing with boats kept in the water for more decades then I will admit to. Have never heard of electrolysis when kept out of the water, as it's all about "stray" currents in the water, which can be from your dock, vessel, or another in the near vicinity. And as I previously stated, both the aluminum and especially the zincs appear fine, and they would be the first effected if kept in the water as was the case with one of mine years ago when zincs were vanishing before even 6 months; but neither bronze props, rudders, or stainless shafts were damaged. Local Marine Electronics company did some testing and best solution was the addition of a Galvanic Isolator on Shore Power One, which generally is the only shore power plugged in 24/7. Since that time 12 month old zincs remain in great condition.
That said; difficult to tell if the very critical area I circled below is in fact "deep pitted," bit if so I would not use prior to being checked out by prop shop. If it's just discolored or dirt of some sort, clean them up and go boating. Their probably, as many others have indicated, stainless with more iron.
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