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sauve · 03-05-2011, 12:30

I have had my new boat maintained by a professional up until this point. I have a fair bit of basic knowledge with diesels but I recently took a Diesel Engine coarse and the instructor said that the heat exchangers that use raw water to cool the freshwater system have zincs that need to be replaced. I can't seem to find them on my engine. The manual doesn't mention them. It is about 3 years old, Yanmar model 4JH4-HTE. I just read that Yanmar freshwater cooled engines don't require zinc replacement. Is this correct?

four winds · 03-05-2011, 12:49

That's what the manual for my 3GM30F says.

The drawings for the fresh water engine do not show the fittings or chamber (terminology?) for the zincs that are shown on the raw water engine drawings.

I think you are good to go.

barnakiel · 03-05-2011, 15:15

To make things more complicated: our fresh / raw exchanger has a zinc and this does get used up. Not only - we get some corrosion issues on the exchanger around the zinc area .... is this so because the zinc should not be there?

(all tubing rubber - no hard parts between the exchanger and the engine ...)

Why?

b.

zeehag · 03-05-2011, 15:23

you will have atleast 2 zincs inside engine-- have large flat head screw spots to unscrew to place them--look again.....you WILL find them...... goood luck.
i am going by my 2 qm 20 h manual---and engine....

siroismi · 03-05-2011, 15:38

Chances are you do not have zinc on your engine.

I do have a Yanmar 4JH3-TE and there is no zinc on it. Hard to believe, but that's it. Back then, I even went on to contact two distributors who confirmed it. Only info I could get from them when I told them I could not figure out how it could be was "... designed that in a way to withstand corrosion..."

Michel

zeehag · 03-05-2011, 15:53

(swallowing words) ok---i kno wthe 2qm20h has 2 of the things in top of engine.....

Loquat · 03-05-2011, 16:18

My new boat 'to me' has a 4jh4 also. I was wondering about the zincs also. I read the manual and is says nothing about zinc replacement. Except, in the maintenance kits section which yanmar sells , there are parts called replacement zincs. I don't have my manual w/me right now but I will look again tomorrow to see what engine the kits we supposed to be for.

barnakiel · 03-05-2011, 16:40

In fact, a Yanmar is all one big zinc ...

;-)
b.

four winds · 03-05-2011, 16:52

My very old Yanmar manual has the 1, 2 ,& 3 cylinder engines. The GM series though, not the newer model of the OP's concern.

On the raw water engines one zinc is located on the rear of the cylinder head right next to the rear lifting loop. This loop shares two bolts with the cover that also holds the zinc. It's not a flat head, rather a large square boss to wrench on.

On the fresh water engine at this location is a simple cover with no zinc installed, held on with four bolts, two shared with the lifting loop.

There is a section for conversion to fresh water as well. In that regard it shows removing the cover with a zinc installed and going back with the plain cover with no zinc. Seems pretty clear to me the GM series fresh water engines don't require a zinc in the engine itself. Can't say that applies to the newer engines however, no experience there.

I installed a new fresh water pump on mine a few weeks ago and was pleased to see crystal clean surfaces inside the water area.

BTW Zee, I think your QM-H series engine is raw water cooled so it would have zincs in the engine.

Mark Johnson · 03-05-2011, 16:53

My Yanmar 2-GM-20-F had no Zincs, or a place to put them. I called right away when installing the thing, and was told that the copper/nickel alloy (Monel?), in the heat exchanger, didn't need it. It has been 15 years. So far so good!

Mark

four winds · 03-05-2011, 17:18

Wow, the OP's engine has four valves per cylinder and a turbo. 110hp.

The maintenance kits I see listed have a footnote concerning the air filter and the zincs which says "not used on all models".

Could be another clue that fresh water Yanmar's don't have zincs.

barnakiel, do have a Yanmar engine? Sounds like you have a "remote" heat exchanger, never seen that.

edit to add, on the raw water GM series the other zincs are located behind the lift pump and secondary filter. One (two total) on the 2 cylinder, and two (three total) on the 3 cylinder. Looking at the fresh water section drawings show nothing in this area. Mine has two large blank plugs there with a recessed drive square for removal.

gbanker · 04-05-2011, 04:52

Just went through this myself. Answer I got was that the metallurgy in the heat exchanger has been changed such that zincs are no longer required for my Yanmar4JH5E.
Contact the manufacturer for requirements for your specific engine.

lancelot9898 · 04-05-2011, 07:16

My Perkins 4-108 (1985 vintage) has never had a zinc. I confirmed this with a Perkins mechanic years ago. The exchanger has rubber end caps and is isolated from the rest of the engine and apparently the dissimilar metals within the exchanger itself does not pose a problem. Only the interior tubes of exchanger contains salt water with the rest of the exchanger contains anti freeze. Note that this anti freeze flows also to the hot water heater and no salt water ever enters the coils of that system so the need for the zinc in that system is questionable too.