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.
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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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.
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.
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
I am now at popcorn stage, contributed bugger all and now sitting back waiting to see all others (extremely valuable) contribute utio s.
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.
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.Originally Posted by Noelm
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.
To be honest I'm not shore I will have a look
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.
Jack.
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.
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.
I'd also test for continuity between the blocks Noel just out of curiosity.
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