Motor anodes

[Noelm]

I just finished doing the annual service on my 90HP Suzuki's, everything went well, BUT, one motor the zincs were very badly eaten, the other motor not so much, and just started kind of wondering why, the motor with the most eaten anodes is also the one the power for the radio, lights and other "stuff" is taken off, could this possibly have anything to do with it? Before anyone starts with funny questions, all accessories are wired correctly, it's a fibreglass boat, there is isolation battery switches, both motors are running fine, it just got me thinking though, why? Even the external anodes are much worse!

[scottar]

Next time your in the water put a volt meter between the two and see what you get.

[Noelm]

Funny you should say that, I was going to do some testing and see if something comes up, it just seems strange that one is so much worse, I guess one way to look at it, they are doing their job! or at least one side is, I will take a photo of them to show how much difference there is.

[scottar]

The suspicion would be that there is no heavy negative between the battery banks or some other resistance in the negatives so as to allow them to not be at the same potential. I have seen similar issues with battery monitoring systems - had a 1.6 volt potential between the negatives of the banks (in this case a house bank) which was sufficient to create charging issues. With the shunts bypassed all was good.

[Noelm]

The motors are on a cat, so two completely different battery setups, controls and everything else, the two motors have nothing in common but the water! The Port motors battery does supply power for all accessories, now that I have just replaced the anodes, I might swap the power source for the accessories and see if the starboard motor exhibits extra wear in a few months rather than the port one.

[scottar]

Might be worth a leakage test too. Low range ammeter in the effected motors negative line, disconnect the positive so there is no chance of the motor itself generating a reading and then start running accessories to see if there is any leakage back through the engine.

As a side note - not the first time I have heard of a Zuke's anodes being almost gone in 12 months. Talking to a well respected Suzuki dealer up here he made specific mention that annual inspection was pretty important too.

[Fed]

Do you have 3 sets of anodes on each motor Noel,.... internal, swivel bracket & leg?
If so are all 3 sets exhibiting the same increased deterioration levels compared to the 'good' motor?

Motors connected together by the steering and possibly the controllers?

Like to guess the hours involved, on a fibreglass trailer boat I'd expect the external anodes to last forever (read a very long time).

[inveratta]

Im not electrically literate......but I do find these sort of things useful to follow through...cos I learn a lot from the wise....the only small offering I have is...is this the side of the boat that has the transponder on it?

[Noelm]

Yep, internal anodes X 3 external near gearcase X 1 and a big one on the bracket, all eaten considerably more than the good motor. Possible common "connection" steering link, binnacle control? salt water when in use, everything else is isolated, seperate batteries with no possible way to connect both, fibreglass boat, I guess if there was only one motor, you wouldn't know or care if one was eating anodes, but having the two kind of gets you thinking.

[Noelm]

Im not electrically literate......but I do find these sort of things useful to follow through...cos I learn a lot from the wise....the only small offering I have is...is this the side of the boat that has the transponder on it?
The one that is good is the side the transducer is on, but not too sure if it is anything to do with it, just to add, I am pretty up to speed with electronics, having been a TV repair guy for years, and a computer support guy, including component level repairs for 20 years, so know my way around test equipment.

[Noelm]

OH, I forgot, motors are at just over 200 hours, first 100 hour service was similar, but really didn't consider anything wrong at that time, Suzuki have service kits, and for some reason, I kept the old boxes with the used parts in them, and labeled them port and starboard, I checked the old anodes yesterday, and that's how I know it was the same at the last service.

[Dignity]

Motors connected together by the steering and possibly the controllers?


Does that mean 2 different power sources but now have a common negative and one of the power sources supplying power to accesories. I have no idea of the ramifications not being electrically literate but using basics of doing one thing at a time to eliminate problems how do you eliminate one or the other to check the theory, connect both motors to one battery as a start maybe and see if the problem still exists.

[Fed]

Does that mean 2 different power sources but now have a common negative and one of the power sources supplying power to accesories. I have no idea of the ramifications not being electrically literate but using basics of doing one thing at a time to eliminate problems how do you eliminate one or the other to check the theory, connect both motors to one battery as a start maybe and see if the problem still exists.
I guess that's what it means Dignity, right now I'm trying to get a 'feel' for it all if you know what I mean.

[Noelm]

OK, photo of anodes from same location, internal in head

[Noelm]

Anode other side

[Noelm]

Those are typical of all anodes from both sides, one side more "used" than the other, now, just touching on Dignity's theory, two batteries, each with a negative connected to the motor directly, both motors electrically connected via steering, we now have an open loop, because neither positive is connected in any way, except maybe when an accessory is running, there is VHF, FM radio, 2 bilge pumps, nav lights and a deck light and the sounder, it could be possible (somehow) for a device switched on, is closing the previous loop/circuit, but even in that case, I don't see a way for that to create some kind of electrolysis to eat away the anodes on one side, but, and it's a big but, probably possible.

[swof63]

Anodes eaten will be current flowing through the anode and electrolytic reaction. Could be current flowing from one motor’s ground to the other via the salt water thus having a positive and negative in that circuit. I’d run both the motors out of the water on muffs and measure voltage between motor grounds see if there’s any at all. Can’t see why it would hurt to tie the earths/negatives of the batts together. Or I may need to pull my head in.


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[Fed]

Great thread Noel, it's going to be a real can of worms when <insert name> gets here.

Out of curiosity I'd hook a Voltmeter from block to block by extending a set of leads and connecting without disturbing the main earth connections, maybe under the starter motor bolts or something.
The last thing you want to do is inadvertently fix it by disturbing a fault without ever finding out what was wrong.

Then of course take it out on the water and see if you can find any Voltage between the motors, be prepared to swap leads at the Voltmeter unless you could be bothered trying to nut out electrolytic vs galvanic, anode vs cathode and current flow vs electron flow... you know the drill.

[Noelm]

Yeah, it is a funny one, as I said, if you had only one motor, there would be nothing to compare, but doing both at the same time, you can see how one is getting eaten away heaps more than the other, I will probably have the boat in the water Monday, but until then I will do some fiddling around and see if I can spot something.

[Muzza]

Probly right off track here, but could it have been an anode quality issue? Are all anodes capable of the same processes thrown at them?
Maybe someone can teach me whether they should all react the same?

PS No, just saw you have multiple anodes on same side with the issue so scratch that.

Apologies just off call, need a fish(and a beer)

Cheers
Muz

[Dignity]

I am now at popcorn stage, contributed bugger all and now sitting back waiting to see all others (extremely valuable) contribute utio s.

[scottar]

Given that there is a probable connection via the steering or control cables, if that connection is insufficient to keep both engines at the same potential, then it is possible it allows enough connection to complete a circuit for very minute current flow - think of the old experiment as a kid of dissimilar metals in an orange. Just a thought.

[TheRealAndy]

The motors are on a cat, so two completely different battery setups, controls and everything else, the two motors have nothing in common but the water! The Port motors battery does supply power for all accessories, now that I have just replaced the anodes, I might swap the power source for the accessories and see if the starboard motor exhibits extra wear in a few months rather than the port one.

The one thing in common is the water between the 2 outboards, meaning one will be an anode and the other a cathode. You need a solid negative link between the 2 batteries so that both outboards are at the same potential.

[SWANY22]

I have the same problem with mine
Have twin 140 on my Haines
And the one on the main
Battery that has every thing off it
The andoe is all way worse

[TheRealAndy]

I have the same problem with mine
Have twin 140 on my Haines
And the one on the main
Battery that has every thing off it
The andoe is all way worse

Do you have a negative link between the 2 start batteries?

Just curios. The boat I own had the same issue according to the previous owner and it had 2 fully isolated batteries. The first thing I did was install a link between the 2. Reading deep into the Yamaha manuals it actually tells you to do this.

I never did look to deeply into measuring the different potential between the 2 negs, but I am curios now. Next time I am on the boat I will remove the link and see if I can measure any difference. I was fortunate in that I studied a semester of corrosion science under a total c#$t of a lecturer at uni, and whilst I did not like the prick, I did learn a lot. My theory was the first thing that came to mind and hence the reason I added the link between the 2 batteries. I just had Spaniard King do a service on the two outboards, and we fitted two new skeg trim anodes so I will keep a close eye on them and see what happens.

BTW, it does not need to be a link between the 2 batteries, it could be a wire joining two convenient points on the outboard depending on the boat setup. The idea simply being that both outboards are at exactly the same electrical potential.

[SWANY22]

Do you have a negative link between the 2 start batteries?

Just curios. The boat I own had the same issue according to the previous owner and it had 2 fully isolated batteries. The first thing I did was install a link between the 2. Reading deep into the Yamaha manuals it actually tells you to do this.

I never did look to deeply into measuring the different potential between the 2 negs, but I am curios now. Next time I am on the boat I will remove the link and see if I can measure any difference. I was fortunate in that I studied a semester of corrosion science under a total c#$t of a lecturer at uni, and whilst I did not like the prick, I did learn a lot. My theory was the first thing that came to mind and hence the reason I added the link between the 2 batteries. I just had Spaniard King do a service on the two outboards, and we fitted two new skeg trim anodes so I will keep a close eye on them and see what happens.

BTW, it does not need to be a link between the 2 batteries, it could be a wire joining two convenient points on the outboard depending on the boat setup. The idea simply being that both outboards are at exactly the same electrical potential.

To be honest I'm not shore I will have a look

[tunaticer]

It could be as simple as the threads in one motors holes for the anode bolts being bare alloy and the other motor painted giving in insufficient grounding. Anodes are worthless if you don't ground them properly.

[Noelm]

OK, I am back online after a horrendous time with our fabulous NBN and offshore support, can't bare to think about it because I want to smash things.....but, I put the boat in the water, measured with both a digital and analogue meters between both motors, in off, key on and running conditions, no difference detected, on either meter! I might just for kicks fit a negative cable between the two batteries as Andy suggested and check in about 6 months time to see if both are roughly the same, stay tuned for an update much later.

[ranmar850]

You have two separate , isolated systems, each running through a single isilation switch so are effectively running it as two single outboards rather than a twin setup? Are you running a House battery--sounds like you don't have a House, just running your electronics through the Start battery on one motor, ie, the one showing the greatest anode loss? You don't have a Parallel (Both) switch in case you need to start one motor off the other battery?
Just getting a mental picture of your setup.

[Fed]

I'd also test for continuity between the blocks Noel just out of curiosity.

[ranmar850]

Andy's idea of an equipotential bond would certainly be worth trying--you don't appear to have an"issue" that requires immediate rectification, just something to keep an eye on.

[Noelm]

You have two separate , isolated systems, each running through a single isilation switch so are effectively running it as two single outboards rather than a twin setup? Are you running a House battery--sounds like you don't have a House, just running your electronics through the Start battery on one motor, ie, the one showing the greatest anode loss? You don't have a Parallel (Both) switch in case you need to start one motor off the other battery?
Just getting a mental picture of your setup.
Correct, two independent systems, if I had a flat battery, I would have to either swap batteries, or use jumper leads, no connection between motors, or switch with "both" no electrical connection except via the water when launched.

[Noelm]

Andy's idea of an equipotential bond would certainly be worth trying--you don't appear to have an"issue" that requires immediate rectification, just something to keep an eye on.
Yes, if I only owned either motor (not twins) I would never suspect anything.

[TheRealPoMo]

OK, I am back online after a horrendous time with our fabulous NBN and offshore support, can't bare to think about it because I want to smash things.....

LOL...I tried telling people not to sell Telecom but they still voted for Johnnie.
If you did then serves you right. If you didn't then cry in your beer like me. Its appalling and....you were warned.

Sent from my SM-G900I using Tapatalk

[The Woo]

Anodes are designed to be sacrificial, so rather than looking for why one is corroded, it might be worth instead looking for why one isn’t corroded?

The corroded one might be simply doing its job as designed. The other, maybe it was not contacting the block cleanly (high resistance between anode and the item it’s protecting renders the anode practically useless).

[Noelm]

Anodes are designed to be sacrificial, so rather than looking for why one is corroded, it might be worth instead looking for why one isn’t corroded?

The corroded one might be simply doing its job as designed. The other, maybe it was not contacting the block cleanly (high resistance between anode and the item it’s protecting renders the anode practically useless).
I did kind of think about this, but, each motor has 3 internal anodes, one external on the gearbox, and one big one on the transom bracket, all are displaying the same condition on the one motor, it would be pretty unlucky for all of them to be suffering bad connections, but not impossible I guess.

[The Woo]

Sorry, missed where you said they were affected similarly.

[TheRealAndy]

Just a though, measure the current between the 2 negatives, not voltage. Its quite possible that the currents are small enough that you cannot measure them with a standard multimeter though.

I am not a betting man, but I would almost put money on this one. I am dying to get on the water and do some tests now. How sad is it that my main motivating reason to put the boat in the water right now is to satisfy my own curiosity about my theory.

[Noelm]

OK, I have access to equipment to measure small current, not exactly sure how there could be current between the negs though, but, it's early in the morning and I need to think about it for a bit.

[ranmar850]

You can have differences in potential between two nominally identical potentials, although the difference should always be small. Any difference will cause the potential for current flow, and this will depend on the magnitude of the difference and the resistance between those points. It's still all Ohms law. I've measured +/- 3 v between the hull of my aluminium fishing boat and the water, alongside a jetty. it changed to less when away from that jetty, using the same multimeter.
When you use an anode to protect anything underwater, its purpose ( obviously ;)) is to be sacrificial, ie, to be eaten away rather than the piece of metal ( motor, hull ) be eaten away in its place. So for it to be eaten away, there needs to be a current flow. Now, whether this current flow is initiated by purely cathodic action ( two dissimilar metals in a conductive solution) or by electrical issues within the installation ( which are accelerating cathodic action)is what we are really speculating about here. At least, this is my understanding of it. Personally, I am always happy when I see anodes disappearing at a rate I would consider acceptable--it just means that they are doing their job. Never happy to pull an internal anode and find nothing but the brass plug, you have sent some time unprotected. We had multiple anodes bolted to the hulls of our allloy crayboats, usually two on the transom, and at least two on the keel. Plus, we would have shaft anodes clamped on the protect the manganese bronze props. All of these weighed at least a kilo each, would be replaced annually and inspected when you came out halfway through the season for a hull clean and paint. You made sure that they were bolted to a clean surface, and, if they wwere just going white and crumbly, it simply meant that they were of the wrong composition, probably not pure enough zinc. The chandlers would quickly pick up on this from complaints and only stock those which eroded and kept clean as they did it.

[TheRealAndy]

OK, I have access to equipment to measure small current, not exactly sure how there could be current between the negs though, but, it's early in the morning and I need to think about it for a bit.

The more I think about this, the more I think I am wrong (re measuring current). There will be some sort of current flow, but I am guessing that with most measuring equipment that the impedance will be too low to actually measure any current flow. The problem then arises when you get some sort instrument with a high impedance the background noise becomes a problem. Its certainly possible to measure current flow in that situation, but I think its totally impractical.

Its been a while since I studied this stuff, but I have been staring at a few equations and tables. I have also been staring at my old text books (which I think have been more useful than the internet). I need to state here that I am making assumptions based on both the material that the outboard and the anode is manufactured from, as well as my very lacking memory on the subject of material and corrosion science.

Anyways, assuming cast aluminum for the outboard, and assuming zinc for the anode, the potential if measured between the outboard and anode is only going to be in region of 0.3V if I got my calculations correct. The actual potential difference between the 2 outboards is going to be significantly less. I have my doubts that its going to be possible to measure any voltage difference between the 2 outboards with any degree of certainty without the use of some sort of specialised equipment.

So I think both you and I are wasting our time trying to measure any difference. However I am certain that having two isolated chunks of metal in seawater will still have sort of potential difference. How much, I have no idea. Its still the most likely reason that both of us (and others) have experienced the same level of increased corrosion on one outboard over the other.

[Noelm]

Yep, I get where you're coming from, everything I measured was seemingly OK?