Home |
Search |
Today's Posts |
#1
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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
|
|||
|
|||
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 |
#7
|
|||
|
|||
|
#8
|
|||
|
|||
Wrong again Larry
|
#9
|
|||
|
|||
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
|
|||
|
|||
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 |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Accident Emergency Question [Three part ] | ASA | |||
Bwahaha! Bye Bye Bushy! | ASA | |||
Mercuiser Ceramic Coated Exhaust Manifold & Elbow Question? | General |