This is related to Yet another Yanmar overheating issue, but is slightly different. I'm at anchor in Placencia, Belize and pulled the end caps off of my 3JH2-TBE heat exchanger. What I found doesn't match any of the 3JH diagrams in the service manual and parts manual. The heat exchanger bundle appears to match that of a 4JH motor, and I'm very confused.
If you look at the diagrams for a 3JH, there only appears to be a single cutout in the outer shell. That makes no sense to me, as how would water flow past the tubes, but I digress. The cutout appears to face downward.
Here's a photo of my heat exchanger tube stack:
If you look at the 4JH manual, you see the following which appears to match what I have:
In the 4JH diagram, there are 2 cut-outs, and they face upwards!
Since I've tried everything known to man (see the original post), other than sacrificing a virgin (parts on back-order, with no known ETA), I'm wondering if somehow I have a hybrid motor that the manual doesn't reflect. For all intents and purposes, I've owned the boat since day 1, so this isn't something that happened that I don't know about.
The running hot issues became worse after I had the engine worked on, which included the heat exchanger being removed and acid-cleaned. I've spent a lot of time talking to the guy who did it, and they admit that they followed the diagrams in the 3JH service manual, not realizing that the diagrams didn't match reality.
The 3JH heat exchanger core has 2 weepholes, which are located at the top. Mine has none, as you wouldn't need any if the large cut-outs face upwards. This would fully explain my overheating, as without weepholes, the top 2/3 of the core would be filled with air, which doesn't conduct much heat.
So, the question is, do I reassemble this to match the 4JH manual (cutouts up)? If so, would the larger cut-out go towards the back of the engine (left side in the diagrams)? The 4JH also has a gasket (44) that I don't have. Is this an issue?
Thanks for any help that you can provide. -- Geoff
If you look at the diagrams for a 3JH, there only appears to be a single cutout in the outer shell. That makes no sense to me, as how would water flow past the tubes, but I digress. The cutout appears to face downward.
Here's a photo of my heat exchanger tube stack:
If you look at the 4JH manual, you see the following which appears to match what I have:
In the 4JH diagram, there are 2 cut-outs, and they face upwards!
Since I've tried everything known to man (see the original post), other than sacrificing a virgin (parts on back-order, with no known ETA), I'm wondering if somehow I have a hybrid motor that the manual doesn't reflect. For all intents and purposes, I've owned the boat since day 1, so this isn't something that happened that I don't know about.
The running hot issues became worse after I had the engine worked on, which included the heat exchanger being removed and acid-cleaned. I've spent a lot of time talking to the guy who did it, and they admit that they followed the diagrams in the 3JH service manual, not realizing that the diagrams didn't match reality.
The 3JH heat exchanger core has 2 weepholes, which are located at the top. Mine has none, as you wouldn't need any if the large cut-outs face upwards. This would fully explain my overheating, as without weepholes, the top 2/3 of the core would be filled with air, which doesn't conduct much heat.
So, the question is, do I reassemble this to match the 4JH manual (cutouts up)? If so, would the larger cut-out go towards the back of the engine (left side in the diagrams)? The 4JH also has a gasket (44) that I don't have. Is this an issue?
Thanks for any help that you can provide. -- Geoff
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