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CapnRon47 11-05-2012 07:39 PM

Yanmar Heat Exchanger/Exhaust Elbow
This is info for those who have not experienced this and a reminder for those who have. I started up my Yanmar 3GM30 after a 3 week layoff, it started fine, but I was not getting much water thru the exhaust. I suspected the inlet strainer, on the thru hull, was dirty or clogged (as we had just experienced some flooding and rough water from "Sandy", but nothing like our friends, neighbors and loved ones up north). But after removing the hose I found that was not the case. And then I remembered about the engine heat exchanger/exhaust elbow. The water from the heat exchanger passes thru a hose loop before it enters the exhaust elbow.

This image shows the rear of the engine and the arrow points to the location on the exhaust elbow where the water enters from the heat exchanger. You can see the beginning of the hose loop just before the arrow (the up hose), the down hose and the plumbing right angle into the exhaust elbow are removed. The plumbing right angle is shown in this next picture:

It is this right angle and the following entrance into the exhaust elbow which usually gets plugged with small pieces of debris. It is pretty easy to remove (access from the side or back) and to clean out both the plumbing fitting and the elbow entrance with a small piece of wire. Once I did this the water out of the boat exhaust was back to normal.

Knowing this and being able to make it right sure beats a trip to the yard!

Prayers and best wishes to those up north!


chef2sail 11-05-2012 07:42 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
Good tip Ron.


capttb 11-05-2012 07:51 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
It kind of annoys me that the elbow is used there, seems an unnecessary restriction on mine.

aa3jy 11-05-2012 08:50 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
16 Attachment(s) where is your anti-siphon hose or am I missing something??

CapnRon47 11-05-2012 09:14 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
I had to remove part of the anti-siphon hose to get it off of the fitting. The first half of the anti-siphon hose is still there, as is the upper U of the loop. The return hose from that U to the plumbing right angle fitting was removed to be able to unscrew the fitting. These were the only pictures I took at the time, so it just shows the situation with the hose and the fitting removed. The inlet fitting, the hose and the U at the top do not seem to collect as much debris or are as restricted as the entry into the exhaust elbow. Local knowledge told me that this is where the blockage usually occurs. If this did not clear the problem, that would have been the next place to check.

thanks, hope I answered your question.

Brent Swain 11-06-2012 06:25 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
Practical Boat Owner magazine said exhaust risers should rise at least 16 inches before any water gets injected. Those Yanmar risers are a joke.

ltgoshen 11-06-2012 08:00 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
When I first got my boat, this is were I found the first leak. You are right it took a lot of looking to find out why the boat was not passing water.

CapnRon47 11-06-2012 08:04 PM

Re: Yanmar Heat Exchanger/Exhaust Elbow
The Yanmar repair manual says:
"The antisiphon Valve is typically fitted between ... the heat exchanger and the exhaust elbow. In certain installations, it may be excluded if the exhaust elbow is above the waterline. Positioning is all dependent on the way the boat builder fitted the engine during the installation."

In Heron, a Clearwater Model 35' Swing keel boat, the waterline is much below the exhaust elbow. I suspect the antisiphon valve is at least 16" above the waterline in our installation, I will have to measure it next time on the boat.


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