Yanmar 3JH2E Heat Exchanger Core Assembly Photos

In How To Remove Yanmar 3JH2E Heat Exchanger, Step-by-Step with Photos, reader John M brought up the orientation of the core assembly within the heat exchanger. There are three things to consider to properly place the core assembly.

But first, the usual disclaimer! I am not a professional mechanic. This is just a record of what I did. It could be entirely wrong. You work on your engine at your own risk. If in any doubt, engage a professional.

  1. The side windows of the core assembly should align with the side openings present in the HE body—this is how the fresh water circulates into the core assembly for the heat exchange to occur.
  2. The side windows on the core assembly are not the same height at each end, meaning there’s also a front and back orientation to it. I believe (I’m not able to confirm at the moment) that the taller side window is for the back. You should be able to compare with the size of the openings present in the HE body.
  3. The gap between the two sets of tubes should be horizontal. This will match up with the horizontal “groove” in the back end cap, to facilitate the circulation of sea water through the tubes.

In other words, for the core assembly to be installed properly, the front and back ends need to be in the right places, and it needs to have the correct rotation within the HE body.

View of core assembly with front end cap removed. Note horizontal orientation of gap between two groups of tubes, and the lack of tubes at the top and bottom.
Core assembly partially removed by tapping the other end with a rubber mallet. The front “side window” is visible, yielding a look at the tubes inside. The side windows on the core assembly align with fresh water openings in the HE body.
Core assembly further removed. The back side window is somewhat visible.
Not visible in this photo, there are openings in the front and back of the HE body that align with the side windows on the core assembly for the cooling fresh water to circulate in the core assembly.

One reply on “Yanmar 3JH2E Heat Exchanger Core Assembly Photos”

Chuck B, Thanx again for a timely reply. These photos and explanation are EXACTLY what I have been combing the WEB for days, trying to find the proper orientation of the HE Cooling Tube. Even the Yanmar Manuals do not have any pics nor description for proper orientation. I’ve spoken to countless “mechanics”, and watched numerous videos to no avail. THANK YOU, for helping Me solve this too long standing conundrum. All the Best. “MRF”

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