90 Etec Corrosion from Stainless propeller???

[gazza2006au]

You have said more than once that it has happend while the engine is in salt water i bet if u put that engine back in salt water and used a multimeter attaching the black to the hull and red to a clean bolt on the engine u would have a positive reading meaning someone has incorrectly wired your engine and u have positive power flowing through the etec your etec is acting like a mentoss in coke

I think a decent mechanic could have rectified it if caught early, one of your tiny red power wires must have been earthed to the engine block to product a lowcurrent of power to slowly eat away the outboard

I rebuilt a 1998 25hp 4 stroke mercury many years ago and i just winged the electrical harness i just assumed the plugs were color coded, we took the boat out into salt water and i heard crackling, zipping,and fizzing i took the boat home and the paint on the bottom of my transom mounts were stripped of paint, i downloaded the manual and i had the tilt trim wires connected in wrongly i had a positive power reading through the block, i correctly wired it and it ran find after that

[Bobpen]

What your saying does not make sense
look at how many thousands of engines are sold with stainless props and are now being sold at 10-15 years old without the issues you have

your barking up the wrong tree blaming the prop in this instance
manufacturing defect or poor maintenance and servicing

Not a trace of corrosion anywhere except in the power head.
Anodes slightly corroded.
Stored on a trailer.
Fibreglass hull.
Hot flushed with muffs every use plus some extras to check it was starting OK.
Batteries isolated.
What maintenance could I possibly have done?
The dealer said it was common and he sees a lot of outboards.
Look at Magnesium, Zinc, Aluminium and Stainless and Galvanic corrosion.
The issue is not a problem for me as my new outboard has a Aluminium propeller.
If people listen to you will you buy them a new outboard when they have problems?
Free advice is worth what you pay for it.

[Bobpen]

What your saying does not make sense
look at how many thousands of engines are sold with stainless props and are now being sold at 10-15 years old without the issues you have

your barking up the wrong tree blaming the prop in this instance
manufacturing defect or poor maintenance and servicing

Always hot flushed with muffs every use plus some extras to check is was starting OK.
Stored on Trailer.
Fibreglass hull.
Batteries Isolated.
No trace of corrosion anywhere visible.
The dealer said it was common.
Not my problem now as my new motor has an Aluminium propeller.
My conscience would trouble me if I told people Stainless propellers were safe.
Still that isn't your problem.
Look at galvanic corrosion Magnesium, Zinc, Aluminium and then Stainless steel.
The aluminium and stainless in the salt water in my glass jar are still fizzing away at room temperature.
I don't need to heat them in a power head.

[Funchy]

Interesting bit of info -


https://www.boatus.com/expert-advice/expert-advice-archive/2012/july/types-of-marine-corrosion

Galvanic corrosion is an electrochemical reaction between two or more different metals. The metals must be different because one must be more chemically active (or less stable) than the others for a reaction to take place. When we talk about galvanic corrosion, we're talking about electrical exchange. All metals have electrical potential because all atoms have electrons, which have an electrochemical charge.
Galvanic corrosion of the more chemically active metal can occur whenever two or more dissimilar metals that are "grounded" (connected by actually touching each other, or through a wire or metal part) are immersed in a conductive solution (any liquid that can transfer electricity). Anything but pure water is conductive. Saltwater, freshwater with high mineral content, and polluted freshwater are very conductive, and conductivity goes up with water temperature. That's one reason why boats in Florida experience more corrosion than boats in Maine.
The simplest example of galvanic corrosion, and the most applicable, is an aluminum lower unit with a stainless steel propeller. The aluminum is the more chemically active metal (the anode), and the stainless steel is the less chemically active metal (the cathode). Several things happen at the same time:

[Bobpen]

The wiring is was all original.
If I wanted to secretly destroy an outboard I would simply replace the zinc anodes with stainless cathodes and let bit fizz.
See where I am going here?

[shaungonemad]

Always hot flushed with muffs every use plus some extras to check is was starting OK.
Stored on Trailer.
Fibreglass hull.
Batteries Isolated.
No trace of corrosion anywhere visible.
The dealer said it was common.
Not my problem now as my new motor has an Aluminium propeller.
My conscience would trouble me if I told people Stainless propellers were safe.
Still that isn't your problem.
Look at galvanic corrosion Magnesium, Zinc, Aluminium and then Stainless steel.
The aluminium and stainless in the salt water in my glass jar are still fizzing away at room temperature.
I don't need to heat them in a power head.

I’m still struggling to understand why the prop is the problem, there are still plenty of other stainless parts on the motor.


Sent from my iPhone using Tapatalk

[Noelm]

No paint bubbling? no other bits corroded through? then I think something else was going on, I don't care what the dealer told you.

[stevej]

You havnt said if it was serviced properly by a dealer

Anodes are designed to break down they can become coated with minerals over time and need a scuff or roughing up to keep working
If they are still full size after many years then there’s your problem

the anodes offset any minor dissimilar metals issues funchy


your theories in stainless props is debunked by how many thousands of engines run stainless props and don’t dissolve power heads

[billfisher]

The wiring is was all original.
If I wanted to secretly destroy an outboard I would simply replace the zinc anodes with stainless cathodes and let bit fizz.
See where I am going here?

Have you checked to see what your prop shaft is made from? If it's stainless steel as well then that put's your prop theory to rest. Also stainless steel forms a protective oxide coating which means in practice it's corrosive effect on less noble metals is lower than it's position on the galvanic table would suggest:

file:///C:/Users/Philip/Downloads/galvanic_corrosion_mby.pdf

[stevej]

Pretty sure the drive shaft is stainless too

If you have serviced it yourself and not replaced the anodes or not noticed them deteriorating then you have your answer

https://www.operatorsguides.brp.com/...16071%20EN.pdf

[Greg P]

Surely has to be more anodes on an Etec that what is in the manual you linked? Do they have them in the block's cooling passages as well like most engines?

[stevej]

It’s all I could find
It’s just a gearbox guide I think and not model specific
my etec detonated before its first service so didn’t get that far involved with it lol

but any engine will dissolve if annodes arnt replaced

[scottar]

Just entertaining the theory for a second, can you explain why the prop would have eaten out the powerhead instead of the gearbox anode directly in front of it or the aluminium in the leg right next to it. Your mechanic is an idiot or a blatant lying crook if that is what he is telling you.

[Noelm]

Yep, kind of agree, I have seen hundreds of boats with stainless props sitting in salt water, and not one ounce of "fizzing" to be seen.

[Bobpen]

What your saying does not make sense
look at how many thousands of engines are sold with stainless props and are now being sold at 10-15 years old without the issues you have

your barking up the wrong tree blaming the prop in this instance
manufacturing defect or poor maintenance and servicing

I have solved my problem. I have an aluminium propeller. You can take your chances, Not my problem.
My anodes were corroding nicely thanks.
The 400 hours were only the hours the engine was running the time fishing at anchor could be 4 times that lets say 1,600 hours with hot or warm seawater in the power head.
Same as being moored for 2 months in seawater.
Anodes cannot protect against corrosion caused by stainless just look a the electron flow.
Feel free to use stainless propellers.
If I sold outboards I would recommend them.
Anyone else be warned your anodes won't protect you.