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dmksails · 30-01-2018, 17:51

My boat has the Yanmar 3GM30F engine. I found in the service manual that there is a zinc located on the cylinder block. Are there any other zincs on the engine or gearbox that I need to be aware of?

RaymondR · 30-01-2018, 20:16

From memory I think there are three zincs screwed into the block of the raw water cooled 3GM30, two on the side and one on the back. None anywhere else.

If the F in the model designation denotes fresh water cooled with a heat exchanger I don't know what they have.

gamayun · 30-01-2018, 22:36

Really?! I was told by a reputable source that there weren't any zincs on my 3GM30F. The service manual that I have covers several different Yanmar engines so do you think that info about the zincs might be referring to something other than the freshwater-cooled 3GM engine?

daletournier · 30-01-2018, 23:00

Quote:

Originally Posted by gamayun

Really?! I was told by a reputable source that there weren't any zincs on my 3GM30F. The service manual that I have covers several different Yanmar engines so do you think that info about the zincs might be referring to something other than the freshwater-cooled 3GM engine?

There are no zincs on the 3gm30f,im sure. I lived intimately with that engine for years.

**Wotname** · 30-01-2018, 23:55

I concur with what is posted above.

No zincs in a 3GM30F
3 zincs in a 3GM30

ggray · 31-01-2018, 17:44

I have a pair of 3GM30F, hitched to sail drives if that makes a difference, and they have zincs in the block. They are European, if that makes a difference.

Vasco · 31-01-2018, 18:13

No zincs on the 30F

ggray · 31-01-2018, 18:28

I seem to be in the minority here!

Actually, I wasn't aware of the zinc (on my motor, at least) until I had to remove the heat exchanger. It wasn't obvious until then.

Seymore · 31-01-2018, 18:31

F means Fresh water cooled, so it doesn't need zincs. There are no zincs.

Change the water annually (I use distilled water) and add anti-corrosive or antifreeze.

ggray · 31-01-2018, 18:37

And I should say that I found little erosion to this zinc even though it must have been 8 - 10 year old.

Replaced it then, but not since.

Perhaps the raw and fresh share the same block, the hole is there, and Yanmar just screws a zinc on the plug.

Or maybe the choice between fresh and raw is made after this point.

Vasco · 31-01-2018, 18:39

The hole is there but no zinc. Sometimes the plug in the hole leaks.

gamayun · 31-01-2018, 20:33

Quote:

Originally Posted by Vasco

The hole is there but no zinc. Sometimes the plug in the hole leaks.

Where? Inside the heat exchanger? Where exactly should I be looking. This is really curious to me.

ggray · 01-02-2018, 03:57

The hole is in the block.

It should be quite visible on a raw water cooled engine, but the heat exchanger makes it hard to see on a FW cooled engine --at least in the narrow hull of my catamaran as my head doesn't get down low.

But the plug in my FW engine (only looked at one) definitely had a zinc screwed onto it. And I am the original owner.