Sacrificial Anodes?

[Wotname]

Originally Posted by Geitz

My 3GM30F (freshwater) does have a zinc. Located on the starboard side of the engine block, tucked just below the heat exchanger, slighly aft. It's a large hex plug screwed into the block. The zinc is screwed into the inside of that plug.

Did it ever need replacing?
Does the engine also have the anodes in the head like the 3GM30?

[Geitz]

I just replaced it last week, but it wasn't missing much material. I'm guessing it was the original from 1999 based on how difficult it was to loosen the plug. There aren't any other anodes that I know of.

[Wotname]

Originally Posted by Geitz

I just replaced it last week, but it wasn't missing much material. I'm guessing it was the original from 1999 based on how difficult it was to loosen the plug. There aren't any other anodes that I know of.

That is to expected - if the information in this link is correct (and I believe it is).
https://www.fisheriessupply.com/unde...ificial-anodes

I hear you about how hard it can be to undo those plugs!

[Geitz]

Originally Posted by Wotname

That is to expected - if the information in this link is correct (and I believe it is).
https://www.fisheriessupply.com/unde...ificial-anodes

I hear you about how hard it can be to undo those plugs!

I had to use a 2 foot, 1/2" drive, breaker bar. Thankfully, I didn't have to add the "torque extender" piece of iron pipe on the end of the breaker bar.

[Wotname]

Originally Posted by Geitz

I had to use a 2 foot, 1/2" drive, breaker bar. Thankfully, I didn't have to add the "torque extender" piece of iron pipe on the end of the breaker bar.

I had to use the torque extender
Maybe I am just wimpy

[Compass790]

Since you have the F version Diane it may be better to think about a coolant change ( if it hasnt been done for a few years) & maybe a heat exchanger clean than worry about the anodes.
If temps are ok you can skip the heat exchanger clean.
Instructions for draining the coolant in the service manual

[djousset]

I guess I need to look deeper into this, first to see if I have the GM20 or GM20F, and then to see if there are anodes (one or two). And perhaps a coolant change..... I'm not sure what to hope for! I'll snap some pics tomorrow.

[Compass790]

Well the conventional thinking is the F version is better to have as the engine runs at a temperature that is better for the engine. Also the the F version doesnt corrode in the block as no seawater circulates through it. You will have the F version or a modification to make it the same as F as Wotname suggested if you have a coolant tank.
But take some pics & post them to put your mind at rest if you cant find the label.
The other advantage of the F version is that you dont have to worry about the zincs but the coolant needs changing every few years. Probably says every 2 years in manual but not needed that frequently IMO.

[djousset]

Finally circling back on this. I looked absolutely e v e r y w h e r e and there is no name plate on this engine. I found a spot where it may have been at one time and I did find a plate (Kanzaki)...transmission? And the name "Yanmar" of course, but nothing noting the model #. Pics attached of coolant fill cap and overflow tank. The search for anodes, and whether or not they need changing will have to wait until spring.

[Compass790]

Well your pictures prove you have the F version as the raw water cooled version has no coolant tank or pressurised coolant twist off cap.


Therefore according to post #17 the anode ( if it even has one, doubtful )wont be an issue so you can sleep easy this winter
It may be as Wottie posted earlier the P.O. converted the engine to coolant cooled & retained the anode or fitted one but its not necessary if you run coolant in the block.
Read his excellent explanation again if in doubt.




If you take coolant cap off when its cold & the coolant looks like rusty water it's time for a change. If its green or pink or yellow its good to go.

[Wotname]

Originally Posted by djousset

Finally circling back on this. I looked absolutely e v e r y w h e r e and there is no name plate on this engine. I found a spot where it may have been at one time ..............

Here is where it should have been.

But as Compass790 posted, it is clearly coolant cooled and his further advice is correct.

[djousset]

[QUOTE=Wotname;3284596]Here is where it should have been.

That's exactly where I expected to find it, there was only a blank plate where a "sticker" may have once been affixed. Thanks for the guidance, I feel more confident about the anodes now.

[mpersena]

I have a westerbeke 30b, fresh water cooled with a zinc on the heat exchanger. I am in salt water and failed to replace the zinc often enough. That caused corrosion on the heat exchanger end cap and quite a leak.

[Compass790]

Originally Posted by mpersena

I have a westerbeke 30b, fresh water cooled with a zinc on the heat exchanger. I am in salt water and failed to replace the zinc often enough. That caused corrosion on the heat exchanger end cap and quite a leak.

Oh yeah if you have a zinc on the heat exchanger sure it needs replacing but I think OP was talking about on the block zincs. If they are on the block they will be in coolant so no worries.
Different case on salt water circuit of heat exchanger.

[boatpoker]

There should be an anode in the heat exchanger. Since salt water flows through the heat exchanger anodes are required to prevent corrosion of the heat exchanger.