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Old 17-10-2012, 15:05   #46
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Re: Yanmar Exhaust Manifold / Heat Exchanger Corrosion

Take it off, clean it well, inspect it and then decide whether you want to replace it or not. Or replace it and keep the old as a spare. If the hose and clamps are good that is all you need to replace. You might want to check/clean the heat exchanger and the vent at the top of the vented loop while you are at it.

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Old 21-10-2012, 19:28   #47
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Re: Yanmar Exhaust Manifold / Heat Exchanger Corrosion

I have similar problem, engineis 6 years old and 1000 hours. corrosion around the end caps, cost new in Aus is $3500.00 most ppl i have spoke to are reluctant to try and weld. I have used metal putty and gasket goo to some sucess, but wonder if its really good enough? It seems yanmar have a big problem with this.
well! actually we have the problem! Any thoughts on what kind of pressure the end caps come under? am i trying to be to fussy? should i stick to the Devcon and gasket goo?. or pay for new $3500 used $2000 or go for aftermarket Bowman approx $1600 with hassle of replumbing etc. Paul.

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Old 21-10-2012, 19:55   #48
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Re: Yanmar Exhaust Manifold / Heat Exchanger Corrosion

This is our 4JH3E exhaust mixer elbow. It is probably not what came from Yanmar. It was on the engine when we got the boat. It is made from stainless steel. I pulled it this year and it was clean inside with no corrosion. This puts me in the "get a good mixing elbow from a third party" camp.


P.S. Sorry for the poor picture quality of my cell phone.
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Old 22-10-2012, 09:09   #49
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Re: Yanmar Exhaust Manifold / Heat Exchanger Corrosion

IMPO I think all the problems with the exchanger and mixing elbows come down to it's initial installation. One has to keep the back flow and back pressure down to the minimum, especially if the motor in at or below the boats waterline.

If one follows the installation instructions completely they shouldn't have a problem. Those loops and diamentions are very important!


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corrosion, exhaust, heat exchanger, yanmar

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