Yanmar Saildrive Burning Zincs!

[RiffRaffSoCal]

Hi! And thanks in advance for anything help.

We have a 2015 Hunter with an SD 25 Yanmar sail drive. We are burning through Zincs in 6 weeks. Had a well respected marine electrician out and he said the system is well/properly grounded but that in his estimation the two ring zinc system is not enough to protect the sail drive.

I’ve called multiple Yanmar service centers and not one of them has reported an issue requiring additional anodes to be added.

No signs of damage to the drive yet - but I’m burning through zincs left and right which is annoying and costly. I’ve changed divers and used different brand zincs just in case.

Also, we confirmed we have a functioning galvanic isolator in place AND we replaced the shore power cable.

At my wits end. Only other item is to haul out and replace then internal pencil anode.

Any ideas?? I’m guessing the electrician could be wrong but I doubt it…and I’m not sure the prop material but perhaps that’s the issue? Don’t know what else to check or try….

Thanks!

[Excalibur5]

First question - are the anodes actually Zinc or are they magnesium alloy? Magnesium is only for freshwater and will erode as you are experiencing if put into salt water as they are much more reactive. Second possible issue would be a very hot marina which can be partially fixed by unplugging shore power. Have you tried unplugging to see if that fixes the issue? If it does, you need either an isolation transformer or a ZincSaver installed on the ground side of your shorepower installation. Last idea I have heard about - if you totally coat the props with an anti-fouling, it will eventually wear off at the tips which can create a battery when the prop is spinning, which would quickly wear down your zincs.

[Excalibur5]

One further idea - if you painted the sail drive with copper-based paint that will cause major issues with corrosion. Make sure there isn't any copper-based anti-fouling touching the saildrive.

[RiffRaffSoCal]

Thanks for this! We have confirmed the correct paint was applied by the yard (who is also an approved Yanmar repair center). Unless they’re lying to me…or made a mistake…

[Calif.Ted]

I know nothing of saildrives but I know So.Cal marina electrical systems, mine's from 1967. Last time I had zincs burn that fast I called management and they found wires serving the whole dock were "compromised" where they had drooped into the water for 50-60 years.

[ggray]

Not to rub salt, but I have gotten as much as 3 1/2 years life on my SD zincs,

Galvanic isolator helped.

[RiffRaffSoCal]

Thanks,

We have a working galvanic isolator installed so I think I’ve ruled out the issue of a hot marina.

I suppose next step is checking the prop and to be sure, unplugging the shore power cord but I think that would take about a month to see if it works without batteries on for bilge - not sure I love that idea….

[sowwaninii]

Been there and had severe electrolysis of saildrive leg. Galvanic isolator works for protecting boat from shore power, but not from stray currents that may be coming from boats in your neighborhood. Need to hang silver chloride probe over side of boat to determine millivoltage in surrounding water. Should be around 950-1100 ma. If under that, might want to hang a sacrificial fish zinc over the side and then take a repeat reading. Check out BoatZincs.com “guide reference electrode and users guide”. Very informative.

[Valmika]

What Marina are you in? Are you in MDR?

[RiffRaffSoCal]

I’m in king harbor./Redondo Beach

Had the marine electrician hang the probes over the end and with a 30 day old zinc was reading 750.

Is there a better temporary fix like hanging an additional anode over the side (that I’d remove from sailing).

We like our slip and hate to move if it doesn’t fix it but that’s an idea….

[sailingchiro]

I was burning through zincs several years ago. (3 months)
For me, I had to find where green and white were hooked together. Green and white should only be hooked together when not on shore power but using house AC, such as inverter and genset. When on shore power, green and white are disconnected.

I took all my greens off the AC panel and did resistance check between green and white. I found 3 sets that were hooked together. Went to the source of the problem and repaired (in my case it was the inverter charger). No more zinc problems. I did recently have a problem and found it to be a Xantrex battery charger. I don't know why yet. I stopped using the charger.
I do know my starboard zinc is eating faster than my port hull but recently have a new neighbor with suspected wiring issues. But my zincs still last about 9 months to a year.

[nortonscove]

I'm with the others saying it's a marina issue. Amazing how many docks are wired incorrectly. I've done work with the company that installs nearly one hundred percent of the new wharves put in in the province and they report that most of the ones they replace have been done incorrectly or have not had sufficient upkeep to remain safe.

[RiffRaffSoCal]

Appreciate the insights! Only question is - wouldn’t other boats near me have the same issue or burning zincs?? All my neighbors say they’re good…9-12 months - granted no sail drives/hunks of metal below water - but typical shaft drive anodes….

I’m so perplexed!

[Midnight Son]

WAG here, was the motor separated from the drive, in the last while? I forget where I saw it, but some drives have insulators on the bolts that attach the motor (iron) to the drive (aluminum), should be one set, to stand drive off from engine, then one set to stand bolts back from engine, thin hard plastic.
Engine drive coupling can be FRP or such, so no conductor. Like I said WAG!
Best wishes all

[RiffRaffSoCal]

Not in the last few years - but I don’t know when the pencil anode was last changed…I could pay $1k for a round trip haul out and anode replacement (cost is that high because while out of water I would want to change Drive oil etc). Worth a shot…