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Stainless duoprop electrolysis

F

fmrosell

New member
"Here is a look at electrolyti

"Here is a look at electrolytic corrosion in a forward stainless steel prop...

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"
 
"wow just pulled mine, gonna t

"wow just pulled mine, gonna take a look at that. were you in a slip where transient voltage could have helped that along?"
 
"Yup!
Lots of tinkering with

"Yup!
Lots of tinkering with the marina wiring back in 2005. These props were new and the boat was maintained at a commercial marina between 2004 and 2006. I then moved the boat to a yacht club where I could do my own maintenance. Yikes! The bellows were breached (XDPs), the props were pitted, they had bottom painted all the underwater metal, they had replaced the exhaust bellows on one drive with the wrong part (different from the opposite drive)...
I took the props to a propeller shop and they welded the outer pitting, but would not touch these spots (fear of melting the clutch). I will post pictures of how they look now, some 3 years later...The pictures above I took in the spring of 2007 prior to fitting out."
 
"Here is the prop just off the

"Here is the prop just off the port drive two days ago...
The repair and paint jobs hold up pretty well in the salt water. It took a lot of work bonding all the underwater metal, painting each spring with the Pettit grey paint, and of course, adding a galvanic isolator to the boat.
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"
 
"Frank
Had my Duo props off l

"Frank
Had my Duo props off last week and noticed the same corrosion on my forward prop. Showed the props to and authorized VP deal and was told it was a defect in the casting. I didn’t give it a thought……….. Sounded logical to me and I thought it was a casting defect myself.. The aft prop showed no signs of corrosion. I have to give it a better inspection when I pull the boat in a few weeks
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"
 
"Don, what did they recommend

"Don, what did they recommend you do, or what would be the expectation of prop durability?

The prop shop guys thought this was electrolysis, but I guess it may be precipitated by an underlying defect in the casting...they advised to use the prop, as it showed no evidence of imbalance or performance loss when they tested it.

In fact they suggestted I repair them like dental work...clean the pits well, fill them with epoxy, sand flush with the surface, and paint over with underwater metal protecion paint.

Every year since, I scrape off the paint in the fall, wire brush, polish and in the spring I paint them again. So far so good."
 
"Frank,
I’m going on my 9th s

"Frank,
I’m going on my 9th season with this set of props. It’s the first time I noticed the cavities on the forward prop. It’s strange that it doesn’t show on the outside of the hub and only on the forward prop. When I pull the boat in a few weeks I’ll bring the props to the local prop shop for evaluation. Your pic’s are clones of the cavities on my props. Leads me to believe it’s a defect in the casting. Some of the cavities are clean and other look like rust . They recommended if it’s not broke don’t fix it.. ………..
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just watch and see if it spreads.
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If you do any kind of repair it might mess with the balance of the prop
I never paint my props just spit shine them. LOL
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"
 
"Don,
I had some pits on one

"Don,
I had some pits on one of the rear props too. I have not scraped off the paint on the remaining props...I will post some pictures. I remember I had to replace the rear prop because the shop melted the clutch and could not fit it with a new one (it was bad and I did not trust it).

It's hard to just spit shine when there is so much fouling that goes on underwater. I don't think I could get the boat on plane if I didn't paint the underwater stuff...

Curious that you recognized the pattern of pits a "clones" of what you saw in your props."
 
"I boat in fresh water lake, a

"I boat in fresh water lake, and have Mg anodes on the boat. I also have a Mg grouper anode hanging in the back of the boat, tied into the bonding system of the boat. My boat is a 2007 Regal 3060 with twin 5.0L OSi with XDP-B drives.

I to had the same problems with my forward (larger) port side prop, however it was getting the holes in through the middle of the blade, you could actually stick a toothpick through the blade. That was in the end of 2008 when I had a haul out to replace bellows under recall. Was sent off to a prop shop and fixed. Not much though of it, but did keep a closer eye on the anodes and such, as I thought this was electrolysis as well.

Then this late summer when the next recall on the bellows came out, during haul out I had holes on the forward props again, however this time on both port and starboard, again both large enough to put toothpicks thru in the middle of a single blade. The VP rep came out and said that there were casting issues and authorized two new forward props. The rear props were in great shape. No other metals under the boat were affected, just the forward props. All the anodes look brand new, along with the Mg grouper anode.

Chris"
 
"Sounds like the dud bellows s

"Sounds like the dud bellows saved you the props...I have posted the pictures on other boards, and everyone thinks this is casting defect....My electrolysis spots looked different and appeared like the steel was dissolving, leaving a pit in the metal shaped like swirls. These were spot welded with stainless steel."
 
some times a bad ground can ca

some times a bad ground can cause the pitting sending power thru your lower and to your props had it happen before
 
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