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.
- 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.
- 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.
- 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.