Where the Heck Does the Yanmar Internal Zinc for the Saildrive Go?

[schoonerdog]

I've got a pencil zinc and for the life of me I can't figure out where this thing goes. I looked at the SD manual (SD20 and SD31) and it has a pointer going to a part of the diagram that's not visible. Everything else is visible in the diagram, just not the part I've got in my hand. I looked at the saildrive itself and know it's "opposite the sea valve". If someone has this saildrive, could they please please please post a picture of this Zinc placement?

Also, I guess you're not supposed to replace this while in the water?

Its a zinc, it should be the simplest thing in the world to see and replace. And since I can't see this thing, I imagine one isn't in place right now. It looks like it just screws in somewhere. Since my lower unit Zincs are deteriorating quickly (read gone) I imagine it's more important than ever to get this done quickly. Actually, I imagine someone just put a threaded bolt into the place where the zinc is supposed to go.

27210-200550 saildrive internal zinc anode

[schoonerdog]

I think I'm tracking down the answer to my own question, there's a large metal blank that I screw this zinc into. Once I remove the blank, water start gushing in, so I work a bit quickly. Assuming I actually unscrew the right piece in the first place. And assuming that my sail drive actually needs one (the local service dealor, bayshore marine in Annapolis said it wasn't needed in the SD31 only the SD20).

"yes honey, there is two feet of water in the boat right now, and no, I really didn't need to pull that plug because it wasn't needed for my unit."

[Vasco]

schoonerdog,

My 3GM30F has a large blank in it too, at the back of the engine. It's where zincs used to go but when I checked with Yanmar they said that engine no longer requires pencil zincs. I found the blank because Yanmar had omitted a gasket and it was leaking anti-freeze.

[schoonerdog]

Rick,

Been checking all around now. The pencil zinc goes in the back of the sail drive, under the black M22 hexagonal nut, inside the unit itself. It's function is to protect the sail drive. This is according to Mack Boring, the US distributor, and Bayshore Marine in annapolis, the local service shop reversed themselves and said it wasn't in the parts book though for the SD31. They did recommend pulling it out, looking at the blank and seeing if there was a place for the zinc to go as the extra protection would be a good thing. I guess that's what I'm going to do then...

[delmarrey]

One could always bond the saildrive to an external zink located in the area, you think???????

[vonotto]

Not to hijack the thread but I have never had a diesel before..what does the zink do?

[Sonosailor]

Originally Posted by vonotto

Not to hijack the thread but I have never had a diesel before..what does the zink do?

Zinc is attached to submerged aluminum to act as a sacrificial anode. As it is less noble than aluminum (check your old high school chemistry text book. It is quite simple.) it will give up electrons more easilythan the aluminum, and release a zinc ion missing the electron. The energy exchange actually inhibits the corrosion of the aluminum, at least until the zinc is used up.

If you guys are still on this, I have a question: I have two 2GM20s on my cat, with the SD20 saildrives. I have the zinc collar on the saildrives at the prop, and the screw-in anodes inboard behind the big bolt-head. Now, the engines themselves have the same big bolt-heads meant for anodes as well. Do the zincs on the saildrives do enough protection, or should the ones on the engines be worried about as well. In my set-up, they are very difficult to get to.

[Whimsical]

I would think the zinc on the motor would be in the fresh water circuit and would help to prevent internal corrosion. Zincs in the seawater would not perform this function.

Mike

[schoonerdog]

Mike,

I think you are right. on the 3JH series there are no engine zincs, but I believe the GM needs them.

Doug

[cal40john]

This thread has drifted from the original saildrive question. I've come up against this before as I own a 3GM30F(non saildrive). I've found the Yanmar Marine Engine Help site to have usefull information. It is run by a Yanmar shop in the UK.

Non saildrive answer:

Yanmarhelp.com Message Forum - Yanmar marine diesel engine help & advice -> 3GM30F zinc anodes?

John

[Sonosailor]

Originally Posted by schoonerdog

I think I'm tracking down the answer to my own question, there's a large metal blank that I screw this zinc into. Once I remove the blank, water start gushing in, so I work a bit quickly. Assuming I actually unscrew the right piece in the first place. And assuming that my sail drive actually needs one (the local service dealor, bayshore marine in Annapolis said it wasn't needed in the SD31 only the SD20).

"yes honey, there is two feet of water in the boat right now, and no, I really didn't need to pull that plug because it wasn't needed for my unit."

With a wine cork at the ready, the anode can be replaced with the boat in the water. The water pressure is't that high. If you're fast, and use the wine cork while you're replacing the anode on the blank, you can replace the anode with much less than a litre of water into the bilge.

[Tony Cain]

Anyone know what size the zinc for saildrive 31 is or part #....?

[paradix]

If you mean the internal pencil zinc, the part number is in post number 1 on this thread: 27210-200550

If you mean the external one for the prop, it's 196420-02652