Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Jeff
 
Posts: n/a
Default Yanmar Exhaust Question

Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular
has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.

I've been thinking that its time to replace the elbows this year.
Here's my question: The mixing elbow, which is made of some light
alloy and thus is wearing down, is screwed onto to the exhaust elbow
(cast iron?) with a connecting nipple. Since the iron parts seem to
be holding up well, can I simple replace mixing elbows, or should I do
the whole system. This would be an easy decision if I though I could
get them apart without destroying them, but I've assumed this would
involve a large bench vise, oversized pipe wrench, and a breaker bar!
Also, the cost is not trivial - the mixing elbows are about $100,
but the exhaust elbows plus the nipples are another $125. (All times
2, of course!)

Plus a follow up question - does anyone know a good source for parts
like this? I tend to use Marine Diesel Direct (Torreson) and I've
also seen OK prices at shipstore.com, but does anyone know of low cost
parts supplier, perhaps in the Boston area? The major distributors,
like Mastry tend to quote list price.

Here's two pics I took a year ago - obviously it hasn't gotten better!
http://www.sv-loki.com/img_0793.jpg
http://www.sv-loki.com/img_0794.jpg
  #2   Report Post  
Marc
 
Posts: n/a
Default

I go thru this every 4 years as a preventative maintenance measure. I
have never replaced the exhaust manifold or nipple, just the mixing
elbow. I just take the assembly down to my auto mechanic and put it in
his vise. A 24" pipe wrench with a 2" cheater does the trick. The
nipple is a combination right and left hand thread. The regional
distributor for Yanmar in your area is Mack Boring. The only low cost
option is ebay when available.



On Thu, 24 Mar 2005 09:01:41 -0500, Jeff
wrote:

Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular
has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.

I've been thinking that its time to replace the elbows this year.
Here's my question: The mixing elbow, which is made of some light
alloy and thus is wearing down, is screwed onto to the exhaust elbow
(cast iron?) with a connecting nipple. Since the iron parts seem to
be holding up well, can I simple replace mixing elbows, or should I do
the whole system. This would be an easy decision if I though I could
get them apart without destroying them, but I've assumed this would
involve a large bench vise, oversized pipe wrench, and a breaker bar!
Also, the cost is not trivial - the mixing elbows are about $100,
but the exhaust elbows plus the nipples are another $125. (All times
2, of course!)

Plus a follow up question - does anyone know a good source for parts
like this? I tend to use Marine Diesel Direct (Torreson) and I've
also seen OK prices at shipstore.com, but does anyone know of low cost
parts supplier, perhaps in the Boston area? The major distributors,
like Mastry tend to quote list price.

Here's two pics I took a year ago - obviously it hasn't gotten better!
http://www.sv-loki.com/img_0793.jpg
http://www.sv-loki.com/img_0794.jpg


  #3   Report Post  
Capt John
 
Posts: n/a
Default


Jeff wrote:
Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular


has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.

I've been thinking that its time to replace the elbows this year.
Here's my question: The mixing elbow, which is made of some light
alloy and thus is wearing down, is screwed onto to the exhaust elbow
(cast iron?) with a connecting nipple. Since the iron parts seem to
be holding up well, can I simple replace mixing elbows, or should I

do
the whole system. This would be an easy decision if I though I could


get them apart without destroying them, but I've assumed this would
involve a large bench vise, oversized pipe wrench, and a breaker bar!


Also, the cost is not trivial - the mixing elbows are about $100,
but the exhaust elbows plus the nipples are another $125. (All times


2, of course!)

Plus a follow up question - does anyone know a good source for parts
like this? I tend to use Marine Diesel Direct (Torreson) and I've
also seen OK prices at shipstore.com, but does anyone know of low

cost
parts supplier, perhaps in the Boston area? The major distributors,
like Mastry tend to quote list price.

Here's two pics I took a year ago - obviously it hasn't gotten

better!
http://www.sv-loki.com/img_0793.jpg
http://www.sv-loki.com/img_0794.jpg


My first question is why are you doing this? I've never heard of
someone doing this before. Their's nothing wrong with checking the
riser for leaks after it's a few years old, and then after that, but
checking for carbon.... Remember, every time you clean it up and expose
nice fresh iron it will rust, the iron covered in carbon is protected.
Are you getting restricted exhaust because of the carbon build up? And
how do you know this?

It's a good idea to give any engine a good long run from time to time.
This helps to burn off excessive carbon, this is the preferred method
of keeping it to a minimum.

  #4   Report Post  
Jeff
 
Posts: n/a
Default

Thanks - I have this sense of deja vu - did you answer a similar
question last year?

Marc wrote:
I go thru this every 4 years as a preventative maintenance measure. I
have never replaced the exhaust manifold or nipple, just the mixing
elbow. I just take the assembly down to my auto mechanic and put it in
his vise. A 24" pipe wrench with a 2" cheater does the trick. The
nipple is a combination right and left hand thread. The regional
distributor for Yanmar in your area is Mack Boring. The only low cost
option is ebay when available.



On Thu, 24 Mar 2005 09:01:41 -0500, Jeff
wrote:


Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular
has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.

I've been thinking that its time to replace the elbows this year.
Here's my question: The mixing elbow, which is made of some light
alloy and thus is wearing down, is screwed onto to the exhaust elbow
(cast iron?) with a connecting nipple. Since the iron parts seem to
be holding up well, can I simple replace mixing elbows, or should I do
the whole system. This would be an easy decision if I though I could
get them apart without destroying them, but I've assumed this would
involve a large bench vise, oversized pipe wrench, and a breaker bar!
Also, the cost is not trivial - the mixing elbows are about $100,
but the exhaust elbows plus the nipples are another $125. (All times
2, of course!)

Plus a follow up question - does anyone know a good source for parts
like this? I tend to use Marine Diesel Direct (Torreson) and I've
also seen OK prices at shipstore.com, but does anyone know of low cost
parts supplier, perhaps in the Boston area? The major distributors,
like Mastry tend to quote list price.

Here's two pics I took a year ago - obviously it hasn't gotten better!
http://www.sv-loki.com/img_0793.jpg
http://www.sv-loki.com/img_0794.jpg



  #5   Report Post  
Jeff
 
Posts: n/a
Default

Capt John wrote:


My first question is why are you doing this? I've never heard of
someone doing this before. Their's nothing wrong with checking the
riser for leaks after it's a few years old, and then after that, but
checking for carbon.... Remember, every time you clean it up and expose
nice fresh iron it will rust, the iron covered in carbon is protected.
Are you getting restricted exhaust because of the carbon build up? And
how do you know this?


The first time it was checked was by a mechanic (at Ashley Marina in
Charleston, SC) who decided it was the likely cause of smoke at high
rpm. Indeed, the mixer was 90% clogged. That was the worst, but each
time I've done it the engine has run cooler and better. The entire
job is pretty quick, an hour or so for both sides.

I'm not sure there is any iron in the mixing elbow - it seems to be an
aluminum alloy. Does any know what it its made of?

As for checking for leaks, eventually they will occur, and likely at
an inopportune time. I'd rather do the work a year or two early than
in the middle of a vacation. The last time I had a mixer go it was
the day before a six week vacation. I would have missed it, but a
friend, while doing some other work, happened to tap it wrench and
started handing up large pieces of metal. It surely would have failed
within a few hours.



It's a good idea to give any engine a good long run from time to time.
This helps to burn off excessive carbon, this is the preferred method
of keeping it to a minimum.


I'd guess that about 70% of my run time is at 2600 RPM or higher.
I'll be interested to see how much buildup I've had in the past year,
since I made a point of revving a bit higher last Summer, at about
3000 rpm when I could.






  #6   Report Post  
 
Posts: n/a
Default

Jeff wrote:
Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular


has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.

I've been thinking that its time to replace the elbows this year.
Here's my question: The mixing elbow, which is made of some light
alloy and thus is wearing down, is screwed onto to the exhaust elbow
(cast iron?) with a connecting nipple. Since the iron parts seem to
be holding up well, can I simple replace mixing elbows, or should I

do
the whole system. This would be an easy decision if I though I could


get them apart without destroying them, but I've assumed this would
involve a large bench vise, oversized pipe wrench, and a breaker bar!


Also, the cost is not trivial - the mixing elbows are about $100,
but the exhaust elbows plus the nipples are another $125. (All times


2, of course!)

Plus a follow up question - does anyone know a good source for parts
like this? I tend to use Marine Diesel Direct (Torreson) and I've
also seen OK prices at shipstore.com, but does anyone know of low

cost
parts supplier, perhaps in the Boston area? The major distributors,
like Mastry tend to quote list price.

Here's two pics I took a year ago - obviously it hasn't gotten

better!
http://www.sv-loki.com/img_0793.jpg
http://www.sv-loki.com/img_0794.jpg


The build up in the elbo is not carbon. I have replaced three of these
on my Yanmar 3GMD which looks just like yours. I inspect the elbo every
500 hours by removeng the exhaust hose and running my finger up pass
the devider to feel the opening. It is the high temperature of the
water that is causing the build up. Only the cast iron mixing elbo
needs to be replaced. Remove the assembly as in your picture and take
it to a shop with a large vise. The elbo and the stainless union are
standard right hand threads. If the elbo does not break lose use a
torch to cut away some of the elbo materal staying away from the union
threads and it will expand and come lose.
Your engine overheat alarm will not sound until the water exiting the
engine heat exchanger exceeds 160 degrees and these deposits are more
likly to form at temperatures above normal engine temperature but below
160 degree exit water temperature. Most Yanmar owners replace the raw
water pump impeller and forget to replace the impeller cam when it is
worn.

From the author of four books on boat refrigeration

http://www.kollomann-marine.com

  #8   Report Post  
 
Posts: n/a
Default

Wrong again Larry

  #9   Report Post  
Capt John
 
Posts: n/a
Default


Jeff wrote:
Capt John wrote:


My first question is why are you doing this? I've never heard of
someone doing this before. Their's nothing wrong with checking the
riser for leaks after it's a few years old, and then after that,

but
checking for carbon.... Remember, every time you clean it up and

expose
nice fresh iron it will rust, the iron covered in carbon is

protected.
Are you getting restricted exhaust because of the carbon build up?

And
how do you know this?


The first time it was checked was by a mechanic (at Ashley Marina in
Charleston, SC) who decided it was the likely cause of smoke at high
rpm. Indeed, the mixer was 90% clogged. That was the worst, but

each
time I've done it the engine has run cooler and better. The entire
job is pretty quick, an hour or so for both sides.

I'm not sure there is any iron in the mixing elbow - it seems to be

an
aluminum alloy. Does any know what it its made of?

As for checking for leaks, eventually they will occur, and likely at
an inopportune time. I'd rather do the work a year or two early than


in the middle of a vacation. The last time I had a mixer go it was
the day before a six week vacation. I would have missed it, but a
friend, while doing some other work, happened to tap it wrench and
started handing up large pieces of metal. It surely would have

failed
within a few hours.



It's a good idea to give any engine a good long run from time to

time.
This helps to burn off excessive carbon, this is the preferred

method
of keeping it to a minimum.


I'd guess that about 70% of my run time is at 2600 RPM or higher.
I'll be interested to see how much buildup I've had in the past year,


since I made a point of revving a bit higher last Summer, at about
3000 rpm when I could.


I've never heard of anything like this kind of clogging. I've seen iron
risers start to really rust up as they start to leak. It sounds like
your building up soot, which is mostly carbon, but it's normally caused
by an engine running too rich. In the case of a turbo charged engine
soot is frequently caused by running the engine at the point that the
turbo is not producing enought boost to get the right air/fuel mixture
for proper combustion (too rich). Running the engine at slightly higher
RPM's, so that the turbo is putting out enought boost, usually cures
the problem. A dead give away to this is a dirty transom, the soot is
building up on the transom. You could also have an injector pump
problem, too much fuel. Or the boat could be over propped, does it
reach the rated RPM's at full throttle?

  #10   Report Post  
Jere Lull
 
Posts: n/a
Default

In article ,
Jeff wrote:

Every few hundred hours I've pulled the exhaust elbows from my
2GM20F's to chip the carbon away. The starboard engine in particular
has a tight turn in the exhaust hose, and since it gets used some at
low rpm for charging, it tends to get some buildup.


Might you be charging at too low an RPM for too long? Either that or you
have an obstruction (that tight turn?) or mis-adjustment. That first pic
is ugly! We have 1200 hours on our 2GM20F and I haven't found any
appreciable carbon. I rarely idle below 1200, as was recommended to me.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Accident Emergency Question [Three part ] Bart Senior ASA 17 July 9th 04 01:16 PM
Bwahaha! Bye Bye Bushy! Bobsprit ASA 1 June 18th 04 10:37 PM
Mercuiser Ceramic Coated Exhaust Manifold & Elbow Question? Tommy M General 2 June 6th 04 04:13 PM


All times are GMT +1. The time now is 04:33 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 BoatBanter.com.
The comments are property of their posters.
 

About Us

"It's about Boats"

 

Copyright © 2017