Heat exchanger orientation on 2GM20F

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Heat exchanger orientation on 2GM20F

Postby Stephen_H » Wed Sep 19, 2018 2:04 am

Recently removed and cleaned the heat exchanger tubes in my Yanmar 2GM20F. It’s back together and I have less seawater flow out the exhaust then previously. Good example of if it ain’t broke don’t fix it. I was wondering if I put the heat exchanger coils in backwards. There are large intake holes on the sides of the cooling tube housing for the fresh water. There’s one hole on one end and two holes on the other. Anyone know which should face foreword and which aft?
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Re: Heat exchanger orientation on 2GM20F

Postby mike cunningham » Wed Sep 19, 2018 12:04 pm

There are a ton of images and drawings online. Have you searched for "Yanmar 2GM20F heat exchanger drawing"

I seem to recall the coil bundle is symmetrical. When you say two holes on one end and one hole on the other, what assembly are you alluding to specifically?
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Re: Heat exchanger orientation on 2GM20F

Postby mike cunningham » Wed Sep 19, 2018 12:07 pm

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Re: Heat exchanger orientation on 2GM20F

Postby Stephen_H » Wed Sep 19, 2018 12:51 pm

The seawater tubes are symmetrical, however if you remove the entire tube assembly from the heat exchanger body there is an aluminum cylinder that spans from the end caps of the tubes. In that cylinder, there are two large holes on one side and one on the other. I didn't make note of what side the two holes were on when removing the assembly. Now, I realized after I posted that the orientation of the holes would have nothing to do with seawater flow, it's where the fresh water enters and exits to cool the exterior of the seawater tubes. But still would be good to know the answer, or if it doesn't matter. The Yanmar service manual doesn't mention it and the exploded parts diagram doesn't show multiple holes on either side. In the video you shared he doesn't remove the cylinder.
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