Could a Stainless P:ropeller cause galvanic corrosion of an Alloy power head.

[Steeler]

Less engagement with the OP the better me thinks.

[shortthenlong]

Do you seriously think there is not enough film of seawater left in the powerhead to conduct electricity?
So why flush motors at all then. How stupid are you?
On another offshore marine project we had some 6 inch plumbing fittings made from Gun Metal.
The Nuts, Bolts and Couplings were all made from the same metal pour to prevent galvanic corrosion from slightly dissimilar mixes of the gun metal.
There are a lot of know nothings on this forum.
Boring but you try to help them .

images (11).jpeg

Turns out we have an alchemist among us

[Dignity]

Do you seriously think there is not enough film of seawater left in the powerhead to conduct electricity?
So why flush motors at all then. How stupid are you?
On another offshore marine project we had some 6 inch plumbing fittings made from Gun Metal.
The Nuts, Bolts and Couplings were all made from the same metal pour to prevent galvanic corrosion from slightly dissimilar mixes of the gun metal.
There are a lot of know nothings on this forum.
Boring but you try to help them .

Now this is the 2nd time you have mentioned "offshore projects" , please let us know what these are, they might add some credibility to your statements so far they have NO credence according ti current scientific knowledge.
What you have probably not realised (about as polite as I can say it), is that many members on here come from some very diverse backgrounds. Whether it be as simple as massive hrs on the water, to people with an enormous scientific and engineering background.
Many have been on this forum for quite a long time and kept their background quiet.
Bobpen, you are spouting in my very humble opinion a lot of garbage and are just stirring the pot. I did say previously that I wouldn't post any more but you did get my goat up. This is my last offer on this subject, pxxs off and let things lie, agree to disagree with everyone , you are $16k worse (probably better) off with a new motor. Go fishing or whatever you do and let the rest of us think about things that really matter.

[Lovey80]

If I had never had a Stainless prop it would have saved me $16,000.

incorrect.

Hope Karma hits your motor AH
I don't have a stainless prop now and never will.
I am capable of LEARNING.

Karma already has hit my motor. It’s a 2008 model that has had a stainless prop on it since new. Flushed properly and serviced properly and is still going strong.

you still haven’t explained, even if your theory is true regarding the galvanic corrosion, how going to an ally propeller is going to help you? Everything you said was causing the anode/cathode/electrolyte scenario STILL exists!!!!

[shakey55]

This is getting way over my head. I’ve a 2000 model Johnson Oceanpro 115 hp that has a SS prop since new. Not the slightest indication of rust whatsoever, anywhere.

I just read an old THT article about a rusting etec and unfortunately he received similar comments as you have been receiving. It’s obviously NOT a common problem and I’m thinking is caused by some stray or badly connected wiring that somehow is causing the electrical field.

https://www.thehulltruth.com/boating...c-engines.html

I’m no expert in this field, but I just think somehow this may be occurring. If I’m way off course with this idea I apologise.


Sent from my iPad using Ausfish forums

[Dirtyfuzz]

Is this the elusive Kerry?

[Dignity]

Is this the elusive Kerry?

I thought it was as did others but his avatar goes back quite a few years. Maybe he is signed on under many aliases.

[fishtragic]

Sooo many rude replies to this poor lost soul. He's asked a question and nobody is constructively trying to help. Mate, just take the drive shaft out and use the outboard without it thus breaking the connection, problem solved!

[EdBerg]

I don't know if my situation has anything to do with outboards as the poster had regards to electrolytic corrosion, but many years ago when I had my 26ft boat it had a sterndrive Mercruiser S/S duoprop leg on it and I left it moored at the marina for a night or two as I was working on the trailer, anyway when I pulled it out and got it back on the trailer I noticed that the props was covered in what I assumed was ally oxide. The anode in the prop hub and ones on the cav plate were chewed up and had lost about 30% of their size. The coating was on the upper surface of the props closest to the anodes. It looked like it had been deposited there like in an electroplating process. The back of the boat had an ally duckboard, S/S legs supports, S/S live bait intake, S/S trim tabs and large ally fuel tank.

I had to scrape off the crud with a chisel and then wire brush it to remove it all. Now I suspect that it may have been stray electricity going into the water from the jetty I was tied up to, anyway I did some research and apparently Mercruiser has some sort of electrical gismo part that you connect up to the battery and to the legs to reduce the corrosion on the legs, It seems that some of their legs are subject to severe corrosion and pitting with quite a few reports of the legs being severely damaged when moored permanently. They deny everything and it may be that there was a bad batch of alloy used to cast their legs so it may be what the original poster motor may have had, was just bad alloy.

Anyway in my case I ran a 1.6mm solid S/S wire to everything metalic outside on the transom including the leg, motor and also the fuel tank and connected them all to the Neg. terminal of the battery to earth them. Spent quite a few nights on the ocean afterwards and when back on the trailer, there were no signs of new corrosion. I certainly didn't moor it back at that marina to test my theory though, but I still suspect that in my case, it was just stray current from the jetty as it happened extremely fast. You just have to wonder with the amount of reports on legs being chewed up if they used a contaminated alloy.

[scottar]

I don't know if my situation has anything to do with outboards as the poster had regards to electrolytic corrosion, but many years ago when I had my 26ft boat it had a sterndrive Mercruiser S/S duoprop leg on it and I left it moored at the marina for a night or two as I was working on the trailer, anyway when I pulled it out and got it back on the trailer I noticed that the props was covered in what I assumed was ally oxide. The anode in the prop hub and ones on the cav plate were chewed up and had lost about 30% of their size. The coating was on the upper surface of the props closest to the anodes. It looked like it had been deposited there like in an electroplating process. The back of the boat had an ally duckboard, S/S legs supports, S/S live bait intake, S/S trim tabs and large ally fuel tank.

.

This does sound like a galvanic reaction - and is similar to what we see with stainless steel strainer baskets in our cooling systems (although not that quick) where the anode material from the anode in the basket to protect the steel housing, is deposited onto the stainless. I suspect your thinking of a marina based issue is correct. The big difference with this in comparison to Bob's is that yours exhibited typical galvanic characteristics - eating away the most reactive metal in a localized reaction. A galvanic reaction doesn't bypass a more reactive metal or the same metal for some distance and set up. It's localized where the metals are in close proximity - the exact reason your prop wasn't uniformly coated in anode material. Did you have shore power connected to charge batteries?

[TheRealAndy]

If one goes back to the first question, "Could a Stainless Propeller cause galvanic corrosion of an Alloy power head.", the answer is yes. In fact, its not a question of 'could', its a confirmed 100% it will.

This is why outboards have sacrificial anodes. The sacrificial anode corrodes before the expensive bits do. Once the anode corrodes sufficiently, the other bits will start corroding.

I wonder how many here realise there is anodes bolted into the powerhead of most outboards to deal with this problem?

[scottar]

If one goes back to the first question, "Could a Stainless Propeller cause galvanic corrosion of an Alloy power head.", the answer is yes. In fact, its not a question of 'could', its a confirmed 100% it will.

This is why outboards have sacrificial anodes. The sacrificial anode corrodes before the expensive bits do. Once the anode corrodes sufficiently, the other bits will start corroding.

I wonder how many here realise there is anodes bolted into the powerhead of most outboards to deal with this problem?

There's no argument that stainless can have a galvanic reaction with aluminium Andy but it's a massive stretch between that and claiming the stainless prop is the cause of a corroded out power head on a motor that has only done 400 odd hours, is fitted with anodes and is stored on a trailer. The anodes not only allow the use of the required metals but also stop the aluminium alloy from literally eating itself away. If it was an entirely galvanic issue, I would be expecting the corrosion to be in the leg (which has been immersed for 1600 hours and is right beside the prop) more so than the power head. There are plenty of different types of aluminium corrosion Aluminium Corrosion | 13 Types Explained | Fractory

[Steeler]

Anyway who gives a toss. The OP asked a question and vehemently opposed any contrary views to his apparent question.

Those who provided alternatives got called #######s so to this entire thread may the AF minders blow the f^&*#r of a thread up and i am going to have a beer and i will get a shitload of change from $16000.00

[scottar]

Anyway who gives a toss. The OP asked a question and vehemently opposed any contrary views to his apparent question.

Those who provided alternatives got called #######s so to this entire thread may the AF minders blow the f^&*#r of a thread up and i am going to have a beer and i will get a shitload of change from $16000.00

Probably enough to buy a nice new shiny stainless steel prop......................

[EdBerg]

This does sound like a galvanic reaction - and is similar to what we see with stainless steel strainer baskets in our cooling systems (although not that quick) where the anode material from the anode in the basket to protect the steel housing, is deposited onto the stainless. I suspect your thinking of a marina based issue is correct. The big difference with this in comparison to Bob's is that yours exhibited typical galvanic characteristics - eating away the most reactive metal in a localized reaction. A galvanic reaction doesn't bypass a more reactive metal or the same metal for some distance and set up. It's localized where the metals are in close proximity - the exact reason your prop wasn't uniformly coated in anode material. Did you have shore power connected to charge batteries?

Actually Scottar, I misworded, I meant Zinc oxide rather than ally oxide, but I think you know what I meant, anyway, no, the boat was locked up everything was switched off, batteries isolated and no shore power. However there were a couple of steel trawlers close to my boat and they may have had their generators running or shore power connected. It just seemed puzzling at the time and since it didn't reoccur either due to me earthing everything, or by the fact I never moored there again so I didn't worry about it any more. But I do remember that the guys in the States had their legs severely chewed and pitted made me think that the legs may have been made from a bad batch of ally alloy, I would assume that they had anodes on their legs as well, so maybe those got chewed off quickly like mine without the owners knowing, which left the legs unprotected.