Yanmar Saildrive Burning Zincs!

[R Hutcheson]

Possibly stray current from a neighboring boat?

[rmhutch59]

Check the ground connection with a meter from the your shore power to the water (ground). Isolators fail around 1.4VDC, should read less than 0.25 volts. Check the from the engine ground to the water with and without the shore power plugged in. should not change.

It is almost always caused by DC current coming in from the shore power ground connection.

[Talbot]

I had the same problem with my SD20s. Lucky to get 3 months.

I changed the galvanic isolator, and added big tear drop anodes directly wired to the engines.

Result 3+ years on SD20 anodes.

[RiffRaffSoCal]

This is really helpful - thanks! Any chance you’ve got a picture of the connection and of the anodes you used? My only concern with additional anodes is that I’ve heard you can have too much zinc protection.

[sowwaninii]

You can indeed have too much anode protection. Again, you need a silver chloride reference electrode hung over the side and measure the mV. Should be 950-1100 mV. I believe you said your mV was ~ 750mV, which means not enough anode.

[Talbot]

Originally Posted by RiffRaffSoCal

This is really helpful - thanks! Any chance you’ve got a picture of the connection and of the anodes you used? My only concern with additional anodes is that I’ve heard you can have too much zinc protection.

I will take a picture inside engine room later this week. I will measure the anode between the two posts inside the boat (boat in water)

[fstbttms]

Originally Posted by RiffRaffSoCal

I’ve heard you can have too much zinc protection.

Pretty difficult to do on a fiberglass sailboat with a saildrive. Unlikely to happen by simply hanging a guppy anode over the side.

[CharlieJ]

Post #35

Again, you need a silver chloride reference electrode hung over the side and measure the mV. Should be 950-1100 mV. I believe you said your mV was ~ 750mV, which means not enough anode.

The correct range is -550mVDC to -1100mVDC per ABYC E-2: Cathodic Protection

As a practical matter, with aluminum components, I try to stay away from the upper (most negative) value due to the amphoteric nature of aluminum.

[CharlieJ]

#1

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

How was this determined? Did he check for electrical bypassing of the GI? Did he check to ensure the N > G resistance is > 25kohms?

This appears to be a classic case of the engineered cathodic protection system (Yanmar anodes) being excessively challenged by a cathodic load that exceeds the capability of the designed anodes. In other words, cathodic protection is leaving your vessel via the safety ground (green) wire.

[RiffRaffSoCal]

Unfortunately I didn’t ask him specifically what he checked as he was doing it but I know he checked the cable, removed and hooked up to the 110 ans 12v panels, the shore power receptacle, and then dropped anode over the side and measured back to different ground points.

Seems like my best path forward is to disconnect from shore power for say a month with a fresh anode and see if we experience the same rate of depletion. I’ll just be sure to not leave battery switch on so nothing drains the batteries other than emergency bilge. Suppose I could always use the engine to recharge if need be.

Second option is to get additional anodes to drop over the side with a ground connection to the sail drive or engine as someone else recommended…

Last option is to either get a second marine electrician out or start reading electrical text books.

[john manning]

Originally Posted by 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!

If this is a marina or other boat issue then do NOT expect surrounding boats to have the same fault. The vessel with the most anode will be the one affected.

[mcon12000]

Originally Posted by RiffRaffSoCal

Unfortunately I didn’t ask him specifically what he checked as he was doing it but I know he checked the cable, removed and hooked up to the 110 ans 12v panels, the shore power receptacle, and then dropped anode over the side and measured back to different ground points.

Seems like my best path forward is to disconnect from shore power for say a month with a fresh anode and see if we experience the same rate of depletion. I’ll just be sure to not leave battery switch on so nothing drains the batteries other than emergency bilge. Suppose I could always use the engine to recharge if need be.

Second option is to get additional anodes to drop over the side with a ground connection to the sail drive or engine as someone else recommended…

Last option is to either get a second marine electrician out or start reading electrical text books.

This is the perfect time to go to the ABYC website and find a certified corrosion expert in your area. Lots of good advice here but the right guy or gal can put this to bed in an hour. Forever.

[RiffRaffSoCal]

This is such a silly good idea. Headed there now - thank you, mcon 12000

[fritzthecat]

Originally Posted by 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!

are you all the time hooked on shorepower? disconnect it ansee what happens: a friend in shelter bay marina, Panama, returned after 6 month to realise, that his yanmar SD 25 WERE eaten up by the marina shore power, grounded over his SD 25es.... disconnect and see what happens