Mixing Elbow

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mik

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Oct 18, 2021, 12:30:15 PM10/18/21
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The mixing elbow on the motor combines the engine exhaust gases and the seawater that has circulated thru the engine and directs them to the muffler and the exhaust outlet.  Unfortunately, because sailboats generally run their engines at low rpms for long periods, carbon from the exhaust builds up in the elbow and ultimately starts constricting the flow putting excessive back pressure on the exhaust.  On my boat the result of this was that the engine would not rev higher than 2200 rpm when giving full throttle in gear.  When it initially happened, I first suspected a fouled prop or a blocked fuel filter but then narrowed it down to a clogged mixing elbow.  Swapping out the new parts was fairly straight forward.  The attached picture is a view from the mixer from the exhaust hose end. My engine has less than 600 hours and I always rev the engine a few times at the end of a sail as prescribed in the Yanmar manual to avoid this from happening.  In the manual, Yanmar also suggests "cleaning" the mixer every 250 hours or one year, whichever comes first.  

PXL_20210921_194451681 (1).jpg

Ken Kloeber

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Oct 18, 2021, 12:39:15 PM10/18/21
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@mlk

Are you cooling with salt or freshwater?

Ken K

Sent from my phone

On Oct 18, 2021, at 12:30 PM, mik <12mi...@gmail.com> wrote:



The mixing elbow on the motor combines the engine exhaust gases and the seawater that has circulated thru the engine and directs them to the muffler and the exhaust outlet.  Unfortunately, because sailboats generally run their engines at low rpms for long periods, carbon from the exhaust builds up in the elbow and ultimately starts constricting the flow putting excessive back pressure on the exhaust.  On my boat the result of this was that the engine would not rev higher than 2200 rpm when giving full throttle in gear.  When it initially happened, I first suspected a fouled prop or a blocked fuel filter but then narrowed it down to a clogged mixing elbow.  Swapping out the new parts was fairly straight forward.  The attached picture is a view from the mixer from the exhaust hose end. My engine has less than 600 hours and I always rev the engine a few times at the end of a sail as prescribed in the Yanmar manual to avoid this from happening.  In the manual, Yanmar also suggests "cleaning" the mixer every 250 hours or one year, whichever comes first.  

<PXL_20210921_194451681 (1).jpg>

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Zach Smith

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Oct 18, 2021, 1:41:11 PM10/18/21
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Are there any 355s that dont use seawater cooled engines? 

Delbert Patterson

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Oct 18, 2021, 3:04:07 PM10/18/21
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Saltwater hard to find on the Great Lakes, so we all use freshwater cooling Emoji



Zach Smith

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Oct 18, 2021, 3:52:40 PM10/18/21
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Lol good point.

Ken Kloeber

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Oct 18, 2021, 4:24:46 PM10/18/21
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Ok, so my question goes to whether the restrictions (somewhat common at the injector wye on "our" (C30, 34, 36) Universal engines) are due to salt deposition from too-high an exhaust temperature.   Obviously not a freshwater lake issue!!
FWIW, our Universals have two TStats; 160F for salt / 180F for fresh.   
 
-Ken

From: catal...@googlegroups.com [mailto:catal...@googlegroups.com] On Behalf Of Zach Smith
Sent: Mon Oct 18, 2021 3:52 PM
To: catal...@googlegroups.com
Subject: Re: [Catalina 355:4287] Mixing Elbow

David Mills

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Oct 18, 2021, 4:32:41 PM10/18/21
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We are in salt water and had the same condition at 500 hrs. Have religiously been running the Yanmar @ 3500 RPMs for 2-3 minutes every couple hours of usage ever since (since about half my time is spent at less than 1800 RPMs). Elbow continues to look great 150 hrs later. I believe it is the salt build up that causes it.

Dave
Island Time
056

On Oct 18, 2021, at 3:24 PM, 'Ken Kloeber' via Catalina355 <catal...@googlegroups.com> wrote:



Delbert Patterson

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Oct 18, 2021, 10:21:22 PM10/18/21
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I have more than 1600 hours since new in fresh water exclusively (Yanmar 3YM30 in a C355).  No mixing elbow problems so far.



ken magida

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Oct 18, 2021, 11:19:06 PM10/18/21
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I run my ym30 in salt water and at about 1200 hours in2019 needed a new elbow. I just had a barnacle buster treatment when hauled because the engine temperature was running up to 20 degrees higher than usual.  

Ken Magida
Forever Young, C355, #46
Sent from my iPad,
An intelligent device which corrects my typing.


On Oct 18, 2021, at 22:21, Delbert Patterson <delbert....@att.net> wrote:



Bob Story

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Oct 19, 2021, 1:49:44 PM10/19/21
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At 1600 hrs earlier this summer I replaced the mixing elbow. I am in fresh water but have done two major trips through salt water: Bahamas and the east coast of Canada and New England amounting to about 6,500 nm. Elbow probably could have gone another season or two but we are doing another Bahamas trip this winter so that it best to change.

-Bob.
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