Heat exchanger orientation on 2GM20F

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Stephen_H
Posts: 16
Joined: Fri Apr 13, 2018 6:35 pm
Location: Edmonds, WA

Heat exchanger orientation on 2GM20F

Post by Stephen_H »

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?
1988 Mull F30 #95
Edmonds, WA

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mike cunningham
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Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Heat exchanger orientation on 2GM20F

Post by mike cunningham »

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?
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

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mike cunningham
Posts: 342
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Heat exchanger orientation on 2GM20F

Post by mike cunningham »

Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

Stephen_H
Posts: 16
Joined: Fri Apr 13, 2018 6:35 pm
Location: Edmonds, WA

Re: Heat exchanger orientation on 2GM20F

Post by Stephen_H »

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.
1988 Mull F30 #95
Edmonds, WA

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