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

[Bobpen]

I am asking for a friend.😉
A more simple question as some people get confused easily
Hypothetically.
A stainless-steel propeller is attached to an aluminium alloy power head by a drive shaft.
The hot seawater from the alloy power head exits the motor through the stainless propeller hub.
Galvanic corrosion occurs when dissimilar metals are connected by an electrolyte.
An example of a marine alloy from Mercury Marine Engines contains tin, copper, zinc, copper, and aluminium
316 Stainless contains iron, chromium, nickel and molybdenum.
What could go wrong?

[shortthenlong]

5a9fec937d8b70ca181d8840faf273c610ffb179975ea6516a5ceeb868f08bd8.jpg

.....

[Dignity]

I am asking for a friend.😉
A more simple question as some people get confused easily
Hypothetically.
A stainless-steel propeller is attached to an aluminium alloy power head by a drive shaft.
The hot seawater from the alloy power head exits the motor through the stainless propeller hub.
Galvanic corrosion occurs when dissimilar metals are connected by an electrolyte.
An example of a marine alloy from Mercury Marine Engines contains tin, copper, zinc, copper, and aluminium
316 Stainless contains iron, chromium, nickel and molybdenum.
What could go wrong?

Ok for my edification as I am simple and easily confused, if the prop hub is SS and it is sitting on a SS shaft how does that exacerbate the so called galvanic reaction that is occurring. Now I do remove my prop regularly and surprisingly there is still always a coating if grease in the splines, maybe that's causing the problem.

[scottar]

Only if you unbolt them both and put them in a jar of electrolyte on your bedside table. 🤦

PS - make sure to unbolt the anodes first or you won't get the desired result

[Bobpen]

Only if you unbolt them both and put them in a jar of electrolyte on your bedside table. 臘

PS - make sure to unbolt the anodes first or you won't get the desired result

It is hard to use the boat with the propeller off.
Have you ever used a boat?

[Bobpen]

Only if you unbolt them both and put them in a jar of electrolyte on your bedside table. 臘

PS - make sure to unbolt the anodes first or you won't get the desired result

The sea water is an electrolyte. Look it up.
When I use the motor it is sea water.
Is there anyone else out there?

[Bobpen]

Ok for my edification as I am simple and easily confused, if the prop hub is SS and it is sitting on a SS shaft how does that exacerbate the so called galvanic reaction that is occurring. Now I do remove my prop regularly and surprisingly there is still always a coating if grease in the splines, maybe that's causing the problem.

The stainless propeller is connected electrically to the power head through the drive shaft it has a giant nut holding it on.
The power head is alloy.
The alloy power head then connects to the stainless propeller though the hot seawater electrolyte which leaves though the stainless propeller hub with the exhaust gases.
The dissimilar metals cause galvanic corrosion.
Simples.,

[billfisher]

The seawater comes into the motor before the propeller so the two aren't connected by electrolyte. In any case the motor isn't running for more than 50 - 100 hours a year for most recreational use which is not a lot of time for corrosion to occur.

[Bobpen]

The seawater comes into the motor before the propeller so the two aren't connected by electrolyte. In any case the motor isn't running for more than 50 - 100 hours a year for most recreational use which is not a lot of time for corrosion to occur.

The hot sea water from the alloy power head exhausts through the stainless propeller.
A direct connection.
I worked out my boat was in seawater for about 1,600 hours before there was enough corrosion to destroy the engine mounts.
Most of those hours the boat was at anchor but the motor was still full of sea water probably still warm.
Anyone else out there?

[Steeler]

Great thread

[Dignity]

The stainless propeller is connected electrically to the power head

This has me totally flummoxed, how?

[gazza2006au]

Is you're "friend" a "nut" that holds the propeller on? I had to clarrify before disorderly calls me a useless tool

[scottar]

It is hard to use the boat with the propeller off.
Have you ever used a boat?

So get a bigger jar and put the whole motor in if you don't want to take the prop off. Do I have to think of everything Bob??????

I only use my boat occasionally .......... you got me there. The rest of the time I have to work..........maintaining a fleet of commercial vessels..............made up of dissimilar metals including aluminium, steel bronze, stainless, copper nickel, cast iron and probably a few others.............that get stored in a giant puddle of electrolyte..............by changing the anodes which protect them against galvanic corrosion among other things...............who would have thought huh.


You are right though Bob........some people do get confused easily.

[Dignity]

Is you're "friend" a "nut" that holds the propeller on? I had to clarrify before disorderly calls me a useless tool

Ha ha, Gazza, I think in this case Disorderly would be laughing alongside with you. I suspect this is a Troll post, especially when he queries whether Scottar who works and spends his off time on the water whether he has been on a boat is laughable.
I actually sent the copy of all these posts to a scientist mate who specialises in metallurgy and has spent 2 seasons in the Antarctic so no fool and he just laughed and did say some rather harsh things and said I was being had, so I'll stop commenting now.

Edit: I see Scottar got in before me.

[Noelm]

The hot sea water from the alloy power head exhausts through the stainless propeller.
A direct connection.
I worked out my boat was in seawater for about 1,600 hours before there was enough corrosion to destroy the engine mounts.
Most of those hours the boat was at anchor but the motor was still full of sea water probably still warm.
Anyone else out there?

interesting you never mentioned your boat was moored in your other thread!