Anodes on Yanmar 3GM

[brian_neale]

Last weekend I eventually managed to get at the anodes on my Yanmar 3GM. Not the easiest job in the world! I did it in the end by taking off the fuel pump and filter, leaving them hanging on the pipes to remove the need for bleeding later, and by bending an oil feed pipe (at least, that's what it looks like) out of the way. The Yanmar-supplied open-ended spanner was nowhere near strong enough for the job, and would not have been long enough anyway, even supposing I could get it squarely on the anode plugs. In the end, I bought a socket, and by extending the T-bar managed to get enough leverage to get them out. Found that they were still in good nick, after all that, but at least I know!

Couple of questions, though. Have other people with 3GM's had similar problems getting at the anodes? And are there only two of them? Marine Power at Bursledon sold me three as part of a "kit" for winter maintenance, but I cannot find the third!

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[snowleopard]

just checked the manual. it's very specific: "the anitcorrosion zinc is installed in the cylinder block and/or cylinder head"!!

from memory there are two, quite close together and one of them is neatly tucked away so you can't get at it with a socket.

there is a third zinc in the saildrive leg if you have one (this is about twice the length of the engine ones) do not remove while boat is afloat!!

my engine is the raw water version , don't know about the 3gm30(f) version.

hope that helps

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[oldsaltoz]

G'day Brian,

You should find he answer here

<A target="_blank" HREF=http://forums.torresen.com/eThreads/view/engines>http://forums.torresen.com/eThreads/view/engines</A>

andavagoodweekend Old Salt Oz /forums/images/icons/cool.gif

 

[steffen]

Hi Brian,
I had the same problems with my 3GM. Managed to get them loose by the same procedure you used with a pipe wrench(is that the right name for the pipe thing that fits a bolt on both ends??) and a 0,7 mtr steel rod. Though i would tear the whole bl..dy engine from its fittings.

There are three anodes in my 3GM: two are on the side, one behind the other and the third is on the back of the engine block above the reduction box. Its fitted in a square cast iron mounting plate secured by four M8 bolts.
Remove the four bolts rather than the plug itself and remove the plug at home in a vice because you probably cannot get enough leverage to get the bastard out on board.
I remounted the plug using teflon tape so they don't get stuck again.
The mounting plate on the back of the block needs a new sealing when refitting.
You need new rubber rings between the anodes and the plugs when refitting.

Happy sailing, Steffen

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[brian_neale]

Thanks for the comments, guys.

My previous 1GM was easy - anode on small plate held on with a couple of bolts. Fiddly due to engine installation, but not difficult. What I found was that greasing the gasket well meant that it came off easily next time. These big plugs are something else! I put them back much less tightly than they were, and they do not seem to leak. I shall have a look for another anode on the back of the engine. Fortunately, I can climb down into the "engine room" and I have a fair bit of room to work. It is Yanmar themselves who make it difficult!

I took a look at the other site mentioned above. Someone there had a problem with a rounded-off anode plug. Someone else suggested drilling it and using an easi-out. I think it might be easier to just change the engine...

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[jfkal]

Your teflon tape is not a good idea. It prevents the anode from doing its job by breaking the electical connection between anode and engine block.
Just thought you want to know ;-))

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[brian_neale]

Teflon tape = gasket and goo as far as conductivity is concerned. I think that the electrical circuit is actually made between the cover, nuts and studs and thence to block. Less direct, but no need for metal-metal contact of plate to block.

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[jfkal]

Th zinc relies on the thread of its stud to make contact to the block. If you insulate the stud (which carriesd the zinc) it renders it useless. Analogy would be painting your shaft anode.

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[brian_neale]

Steffen - thanks for the pointer. I found the third anode! Having bought a really chunky 24mm socket, I was able to get the plug out on board - no need to remove the cast iron plate. Fortunately, the "engine room" on my boat is accessible via a big cockpit hatch and there is really good access to the back of the engine. Still needed the T-bar plus an extension on that to get enough leverage, but there was enough room to do so. I put all anodes in with a little less torque than they had from the factory, so I am optimistic that it will be a little easier next time. In fact, the anodes were barely used, having only been for half a season, so a quick scrape to get the muck off them and back they went.

I did not use teflon tape, as the plugs need metal-to-metal contact with the block (as per replies above - my reference to gaskets etc was misleading because I was thinking about my previous 1GM at the time which has a different mounting arrangement). You may want to reconsider that approach. I presume that the threads on the plug or the block are tapered, and they seem to seal OK without having to crank them up super-tight.

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