Zincs for SD 20 Saildrives

[davecalvert]

Has anyone had problems with the new two piece zincs for the Yanmar SD 20 saildrives? I converted to these new two piece ones, on our Belize 43 cat, and they are shot after 6 weeks. The old larger one piece ones looked fine after 14 months.

[2Hulls]

Perhaps the old ones weren't making good contact and it was those you really had a problem with but didn't know it?

[chris in SG]

Supplementary question - local agent for Yanmar insists that they only sell aluminium 'zincs' now for SD20 saildrives. Ive used these for 18 months now and they are not depleting much (predictable perhaps) but I have suffered excessive bubbling of paint on the drive leg.

I'm not just taking the agent's word for it. I've read elsewhere that aluminium works fine as a sacrificial anode and is now the recommended material. Any other similar experiences?

[admiralslater]

I had heard that ther are different ones for brackish water .Idont know if that might be the issue

[Double-Wide]

I used the 2 part zincs from "Boatzincs.com" for four years without problems. Has something changed with the electrical connect to shore power?



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[fstbttms]

I have installed hundreds of the 2-pc Yanmar saildrive anodes over the years, both zinc and aluminum. They all seem to perform well and last a long time. I suspect the OP has some issue other than one attributable to the anode.

[simmo]

I just replaced mine a few days ago in Noumea. But I bought the "zincs" from a Yanmar dealer in NZ a few months ago. The new ones I bought are aluminium.

[davecalvert]

I replaced my damaged knew with new two piece aluminum and they are already bad after one month
Can anyone help with advice on what to do to correct this issue? I assume it has something to do with grounding but don't know where to start. Thanks, Dave



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[DotDun]

I assume you are plugged into shorepower in a marina???

What new boat showed up at the time your problem started?

Check to see if you have current flow on the shorepower ground wire.

[davecalvert]

No, we are in the Bahamas anchored out, we have not been in a marina sense I installed the new zincs. The old one piece knew were OK after 14 months.

[GordMay]

“... The engine and saildrive must be connected to the boat’s bonding system. Yanmar saildrives are equipped with a single sacrificial anode that is mounted between the propeller and the drive output shaft housing. The anode is sized to protect the drive ONLY. In most cases additional sacrificial anodes will need to be added to the boat to properly protect the other metal underwater hardware installed on the boat and protect against overloading the saildrive anode. If a bronze propeller is installed on the saildrive additional sacrificial anodes may be needed to maintain the hull potential within safe limits ...”

See Yanmar's Advisdory ➥ http://us.yanmar.com/media/ext/uploa...0Corrosion.pdf

Ed Sherman also has an excellent article on the subject
➥ Portecting your Saildrive | Cruising World

[ggray]

This is a lot of good information.

To achieve a good electrical contact between the "zinc" and the sail drive (as I have seen a good bit of corrosion and scale there), would it be advisable to smear some water resistant grease on the connecting face, like on battery terminals? I used to assume the bolts would be the conductor, but I've since learned that SS is not the best conductor. 'Though perhaps it's good enough with the voltage involved.

Just trying to help my sail drives as much as I can! Since I installed a galvanic isolator, I can't complain about the life of my zincs. This haul out was delayed, and the zincs were 3 1/2 years in service. Still a lot of zinc left.

[rancher44]

I have just had to replace my sail drives because of the electrolosis. I have put an isolator and found zinic zinics and will replace the aluminium ones . they did not last any time .
Now the SD-20's are not available and are replaced by SD 25'S
Also the price is now 4300 for a sail drive

[fstbttms]

Originally Posted by rancher44

I have just had to replace my sail drives because of the electrolosis. I have put an isolator and found zinic zinics and will replace the aluminium ones . they did not last any time .
Now the SD-20's are not available and are replaced by SD 25'S
Also the price is now 4300 for a sail drive

No regular in-water hull cleanings by a diver who would've alerted you to the corrosion issue?

[rancher44]

we were actually cleaning the bottom every month and replaced zinics every other month.