Heat Exchanger Zincs Not Required ?

[MV-Romnya]

Thanks Lancelot9898 my heat exchanger on the Perkins 4.108 has rubber caps between at both ends so there is no metal from the raw water system to the engine at the heat exchanger - but the water pump">raw water pump is attached to the engine - so the question is what stops the electrolysis - i am replacing my raw water pump because it is green with corrosion - any suggestions and comments will be much appreciated thanks - MVR

[lancelot9898]

My 4-108 Perkins is bonded to the hull zincs and also the prop zinc. Also all the bronze thur hulls are bonded, but there are differing opinions an doing that.

[MV-Romnya]

Thanks again Lancelot9898, I am trying to find how to bond the new bronz thru hull I am about to install - can you point me in the correct direction or can you make comment - the boat is a wooden hull and has zink attached to the metal rudder under water - Karl

[L124C]

I contacted List Marine, a local yanmar dealer with sharp mechanics. They confirmed that a zinc is not necessary in the heat exchanger, because all dissimilar metals are separated by gaskets.

[kenbo]

Originally Posted by L124C

I contacted List Marine, a local yanmar dealer with sharp mechanics. They confirmed that a zinc is not necessary in the heat exchanger, because all dissimilar metals are separated by gaskets.

Wait until the end caps on the heat exchanger are removed a few years from now and you see the aluminum alloy heat exchanger wasted away. And they don't use gaskets but rather a thin o-ring that fully compresses and allows the bronze end cap to contact the aluminum heat exchanger.

Dry assembly hastens the corrosion.

And what about the bolts that go through the end cap and into the heat exchanger, they aren't electrically isolated.

Real sharp mechanics I'd say!

[L124C]

Originally Posted by kenbo

Wait until the end caps on the heat exchanger are removed a few years from now and you see the aluminum alloy heat exchanger wasted away. And they don't use gaskets but rather a thin o-ring that fully compresses and allows the bronze end cap to contact the aluminum heat exchanger.Dry assembly hastens the corrosion.
And what about the bolts that go through the end cap and into the heat exchanger, they aren't electrically isolated.
Real sharp mechanics I'd say!

Have pictures of the alleged carnage? I'll ask them! They are knowledgeable, have saved me money in the past, and have more work than they need. I don't know why they would mislead me!

[Training Wheels]

Originally Posted by kenbo

Wait until the end caps on the heat exchanger are removed a few years from now and you see the aluminum alloy heat exchanger wasted away. And they don't use gaskets but rather a thin o-ring that fully compresses and allows the bronze end cap to contact the aluminum heat exchanger.

Dry assembly hastens the corrosion.

And what about the bolts that go through the end cap and into the heat exchanger, they aren't electrically isolated.

Real sharp mechanics I'd say!

Hmmm…..mine is over 20 years old, and I had it apart last year and everything looked great.

[kenbo]

Yanmar wouldn't be in business if they made terrible engines, they don't. And every HX isn't going to corrode to pieces. What got me was the sharp mechanics saying everything was isolated by gaskets when Yanmar doesn't use gaskets in the wet end assembly and the fact that the end cap bolts tie all the dissimilar metals together without isolation.

The seats that the o-rings sit in on the aluminum HX are what tends to corrode in my experience. I've restored that groove on dozens of Yanmars but some can be too far gone to save and the entire manicooler has to be replaced.

Typically the problem exists on engines with electrical issues like a bad bridge rectifier on the alternator, or a small current leak on an oil pressure switch. On Yanmars installed on aluminum vessels where they are fully electrically isolated you don't see the corrosion issues as often. The other protection that Yanmar relies on in lieu of anode protection is flushing and changing the ELC coolant every two years. And we know that Yanmar owners do that, right?

I don't have a dog in this fight but it always troubles me when supposed experienced mechanics give patronizing answers to less informed owners. Ever ask a Yanmar technician why the JH series doesn't have an air filter, the answers are downright laughable.

[Compass790]

Originally Posted by kenbo

Yanmar wouldn't be in business if they made terrible engines, they don't. And every HX isn't going to corrode to pieces. What got me was the sharp mechanics saying everything was isolated by gaskets when Yanmar doesn't use gaskets in the wet end assembly and the fact that the end cap bolts tie all the dissimilar metals together without isolation.

The seats that the o-rings sit in on the aluminum HX are what tends to corrode in my experience. I've restored that groove on dozens of Yanmars but some can be too far gone to save and the entire manicooler has to be replaced.

Typically the problem exists on engines with electrical issues like a bad bridge rectifier on the alternator, or a small current leak on an oil pressure switch. On Yanmars installed on aluminum vessels where they are fully electrically isolated you don't see the corrosion issues as often. The other protection that Yanmar relies on in lieu of anode protection is flushing and changing the ELC coolant every two years. And we know that Yanmar owners do that, right?

I don't have a dog in this fight but it always troubles me when supposed experienced mechanics give patronizing answers to less informed owners. Ever ask a Yanmar technician why the JH series doesn't have an air filter, the answers are downright laughable.

Completely agree Kenbo! Enjoyed your post telling it like it is.

My dealings with some Yanmar professionals havent filled me with confidence. They are used to dealing with people that know less than them & fall over when questioned about Yanmar deficiencies.
Not that I'm saying any other brands mechanics would be any different.
Most of them just parrot the bosses BS tho they probably need to to stay employed.

[Wotname]

(sigh) Another necro-thread resuscitated. The correct answers were posted on the first page but let me recap - it depends!

It depends on the materials used to fabricate the heat exchanger. If it constructed from cupronickel, it does not need zincs. Do your own research if you don't believe it.

Yanmar used cupronickel for some of their heat exchangers and these ones do not have have zincs.

Yanmar designers occasionally did a few things wrong but this isn't one of them. I am no friend on the Yanmar pricing department but mostly their designers were on the money; at least they were in the past when they designed their engines to last. I'm not sure I have faith in the newer designs but I will have to wait and see I suppose.

[Training Wheels]

Originally Posted by Wotname

.



Yanmar designers occasionally did a few things wrong but this isn't one of them.

Yeah, I curse them about the raw water pump facing so that you have to pull the pump to check the impeller. And then there’s that coolant pump that you can’t rebuild because you have to destroy it to get it apart.

No problems issues with the heat exchanger though.

[Wotname]

Originally Posted by Training Wheels

Yeah, I curse them about the raw water pump facing so that you have to pull the pump to check the impeller. And then there’s that coolant pump that you can’t rebuild because you have to destroy it to get it apart.

No problems issues with the heat exchanger though.

To say nothing of their exhaust elbows...

But hey, their raw water cooled cast iron blocks last (almost) for ever if you keep the zincs up and flush them occasionally.

[kenbo]

Originally Posted by Wotname

(sigh) Another necro-thread resuscitated. The correct answers were posted on the first page but let me recap - it depends!

It depends on the materials used to fabricate the heat exchanger. If it constructed from cupronickel, it does not need zincs. Do your own research if you don't believe it.

Yanmar used cupronickel for some of their heat exchangers and these ones do not have have zincs.

Yanmar designers occasionally did a few things wrong but this isn't one of them. I am no friend on the Yanmar pricing department but mostly their designers were on the money; at least they were in the past when they designed their engines to last. I'm not sure I have faith in the newer designs but I will have to wait and see I suppose.

Wottie,

I don't disagree that the tube stack is cupronickel and as such will be long-lived. But the manicooler housing where the tube stack lives is made of aluminum alloy. The end caps on the HX are bronze and are attached by SS bolts into the aluminum alloy HX. This is where corrosion can occur. Just like a SS fastener in a mast it should not be assembled dry. I use TefGel but Lanocote or similar would help as well.

I also did not raise this thread from the dead but was responding to a post made yesterday.

[L124C]

It always makes me laugh when people comment on, or "sigh" about stale threads on a forum that embraces technology that was first developed a thousand years ago!

Sure, there were some theories on the first page that seemed credible. There was also a sarcastic reference to Yanmar motors as being "one big zinc". One of the first references I've heard about Yanmar, implying they were badly designed and short-lived! So, the question is, how do you separate the wheat from the chaff on the internet?

So, I contacted Yanmar mechanics that I've dealt with and respect. (By the way most mechanics are dealing with people that "know less than they do", or they wouldn't need a mechanic! You know who needs the assistance of a professional who knows as much as they do? A brain surgeon!).
I take the time to report my findings to this dead thread.

"Kenbo" responds with contrary predictions of gloom and doom, and takes a shot at the mechanic in the process!
I asked Kenbo if he can document the carnage. If so, I'll contact the mechanic to explain why the "gaskets" didn't work. If the mechanic is blowing smoke or dumbing it down, I'd certainly like to know about it!
"Trainingwheels" chimes in, contradicting Kenbo, reporting his 20-year-old heat exchanger is alive and well.
Then, "Wotname" extends the dead thread, chastising me for reviving it, and stating that the simple answer is on page one! Seems to me that if the metal used was the answer for my specific HX, the mechanic would have told me that. Seems more formidable than "gaskets"!
So forgive me for not accepting the word of anonymous forum participants with unknown credentials, going to a bonafide professional, and reporting his response.

I'm still trying to adjust to the fact that the 2020 election was "rigged", and now I find out my heat exchanger was designed by a bunch of knuckleheads, and my mechanic is one of them! I'll never doubt anything I read on the web again!🤪

[Wotname]

Originally Posted by L124C

It always makes me laugh when people comment on, or "sigh" about stale threads on a forum that embraces technology that was first developed a thousand years ago!

Sure, there were some theories on the first page that seemed credible. There was also a sarcastic reference to Yanmar motors as being "one big zinc". One of the first references I've heard about Yanmar, implying they were badly designed and short-lived! So, the question is, how do you separate the wheat from the chaff on the internet?

So, I contacted Yanmar mechanics that I've dealt with and respect. (By the way most mechanics are dealing with people that "know less than they do", or they wouldn't need a mechanic! You know who needs the assistance of a professional who knows as much as they do? A brain surgeon!).
I take the time to report my findings to this dead thread.

"Kenbo" responds with contrary predictions of gloom and doom, and takes a shot at the mechanic in the process!
I asked Kenbo if he can document the carnage. If so, I'll contact the mechanic to explain why the "gaskets" didn't work. If the mechanic is blowing smoke or dumbing it down, I'd certainly like to know about it!
"Trainingwheels" chimes in, contradicting Kenbo, reporting his 20-year-old heat exchanger is alive and well.
Then, "Wotname" extends the dead thread, chastising me for reviving it, and stating that the simple answer is on page one! Seems to me that if the metal used was the answer for my specific HX, the mechanic would have told me that. Seems more formidable than "gaskets"!
So forgive me for not accepting the word of anonymous forum participants with unknown credentials, going to a bonafide professional, and reporting his response.

I'm still trying to adjust to the fact that the 2020 election was "rigged", and now I find out my heat exchanger was designed by a bunch of knuckleheads, and my mechanic is one of them! I'll never doubt anything I read on the web again!🤪

My apologies to L124C. My sigh was never intended as a chastisement to him but as it perceived as such, I need to polish my writing skills. However it did cause you to laugh so that isn't a bad thing is it?

It was more an exasperation on my part that even after a passage of 10 years, the answers to the OP's question are all over the shop.

Although the OP hasn't been back since 2013, let's revisit the original question. The OP stated "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?.

Let's leave aside all the internet comment from all and sundry and go straight to the printed (and published) word of the manufacturer - the service manual. Note, I can't vouch for the veracity of the Yanmar service manual but I reckon it is a good starting point and for those who wish to disagree with, take it up with Yanmar. I am using rev 2 dated Jul, 2007; there may be later revisions but I don't have access to them.

The service manual I have clearly states and gives the location of the zinc anode in the sea water side of the cooling system for the 4JH4-HTE. It requires the zinc to be replaced every 250 hours. Note the 3JH4E and the 4JH4AE which are covered by the same manual do not have zincs however the 4JH4TE does (just the same as the 4JH4HTE.

I also note on the 4JH4 series, there are O rings and gaskets for the end caps yet one end of the 3JH4 does not have a gasket.

Maybe if anyone is talking to their Yanmar certified mechanics (sharp or otherwise) they can ask why the differences mentioned above occur. My guess is they won't know but like many, they will give you an answer anyway.

Maybe the manual is wrong .