Yanmar 4JH5E heat exchange failure

[David Hibbard]

We re-powered our 40 sailboat with a Yanmar 4JH5E 54hsp in 2015.
As winter sailors in the EC we flush the sea water out with tap water each time we put the boat on the hard March-November.
When we last used the boat winter 2020, the fresh water heat exchanger failed. The wall between heat exchanger and the seawater cooling system had rusted through.
The engine had 18 months of use and 600 hours on it.
Does this failure seem premature to anyone?
Has anyone experienced the same problem?

[tkeithlu]

Definitely premature. Now for the cause. A likely source is not having zincs in the system. That interface should not rust, period.

[David Hibbard]

Apparently the 4JH5E does not have sacrificial zincs.
One service department said that the Yanmar designers places rubber gaskets between different metals to deal with the corrosion potential. ??

[sailormed]

David Hibbard:”The wall between heat exchanger and the seawater cooling system had rusted through”.
I took apart, cleaned and reassembled the HE on our 3JH4E this 2021 spring.

I do not understand the “rusting” of the heat Yanmar exchanger. On the one I took apart the body holding the tubes as well as the end caps are a of copper based alloy. I suppose Yanmar selected these materials for their resistance to electrolysis. Copper does not rust.

Copper bronze and brass are all way higher in the Galvanic Table then the iron or eventually aluminium of your engine, so the engine block should be sacrified before the HE.

Maybe your engine has a HE that is not an original Yanmar HE installed by a previous owner?

[Lepke]

The rubber doesn't do squat. It might actually be less damaging w/o the rubber. When I run into an engine w/o a zinc, I add them. All the metal in the salt water path needs to have a metal connection to the zinc or zincs in bigger systems. Sections of plumbing separated by hose needs a ground wire connection or a separate zinc.

[more]

¸What you talking, what wall do you think Cupronickel tube where salt water passing.this is easy repair if only couple pipe is broken. But all this part with sea water pipe pas can buy new 1000$+-
if body of heat exchanger is broken,also possible repair with welding or Brazing Cast Iron is tricky but possible.
Put a picture here. I repair volvo penta heat exchanger missing 100 gram of aluminum.

https://www.youtube.com/watch?v=ZV6O8LIiW6w

[David Hibbard]

Thanks guys, I’ll be at the boat in 2 weeks and will provide more details then.

[David Hibbard]

https://drive.google.com/file/d/1nj5...ew?usp=sharing
I promised to return to this discussion once back on the boat and with the failed part in hand. The above link provides a picture of the exhaust manifold showing the area which corroded to the point of a hole into the fresh water system.
I have talked with a few diesel mechanics here in Antigua about this issue.
The first reasoned that there is a depression built into the EM of the 4JH5E which allows acidic exhaust gas to pool. Over time this design flaw becomes a small crater accentuating the corrosion.
Another diesel mechanic sited galvanic corrosion. The weld material used is dissimilar to the cast aluminum leading to the reduction in material at this location and further supporting the first theory
The solution with long term storage would be the dismantling of the EM flange from the mixing bowl. All in, very disappointing with a relatively new Yanmar 4JH5E diesel engine which is build without sacrificial zincs.
Further comments are welcome.

[jt11791]

That HX looks pretty bad. You wrote that you flush with fresh water at the end of the season. Do you also flush with some type of antifreeze/preservative? Leaving plain water in there may allow corrosion to continue during the off season.