Exhaust Riser Time Bomb

G

gonzo

Member
Joined
Dec 11, 2010
Messages
22
Fluid Motion Model
C-24 C SE
Hull Identification Number
fmlt2113a606
Vessel Name
Lara
MMSI Number
CF0309 TH
Hi Im new here. I just bought a 2006 Ranger 21EC.

The first thing I did was change the exhaust riser. Even though it only has 100 hours on the meter but not knowing the history, I figured I better. Ive learned tough lessons with this part. After only 4 years there were large flakes of rust falling out of it and the exhaust passage was some what restricted with chunks of rusted cast iron erupting from the walls.

Im surprised that no one is talking risers here. When this part fails it WILL destroy your entire engine. As in hydraulic locked cracked cylinder walls. Yanmar says to remove and replace annually, some say every 5 years in salt water even if flushed, and 10 years for fresh water. I plan on every 5 years here on the California coast.

It is an easy job. For the 3YM30 the part cost $160. Remove the exhaust assembly from the engine. Separating the exhaust pipe from the riser is tough. The threads are rusted together big time. I used a torch, a large vice,a piece of pipe, and a block of wood with a hammer all at the same time and voila it broke loose.

I guess most of these boats are less than 5 years old but I just thought I would pass some wisdom along seeing that no one here is talking about them. Replace your risers friends.
 
I am not sure about the R21 engines but I thought the riser on the larger Yanmars found in the R25s were alloy. Still needs routine inspection and replacement but I would not expect alloy to fail in same manner as cast iron.
 
Hi Gonzo,
Thanks for bringing a maintenance issue to the board. Maintenance, and how to better care for our tugs always excites me and gives me something on this site I can sink my teeth into. It is always good to stress how important it is to do these simple inspections and replacements if needed. As you said the cost is huge if it is overlooked. So once again, Thank You for bringing it up!

I have a R-29 and I am coming up on my 250 hour service. I do all of my own servicing. One of the things that is up for me on this service is to inspect the exhaust mixing elbow. They say it is to be done once a year or every 250 hours.
This will be my first time doing the inspection but it does not look like it will be any trouble.

This is one of those very important maintenance issues that cannot be over looked. I will be reporting the results of my inspection and how to do it as soon as I get it done. That should be mid January sometime, for those with R-29's that want to know.


Welcome to the Ranger family. I see that you are out of Ventura. My boat at this time is down at channel islands harbor. I do not store it in the water. I have a trailer and store it close by the launch ramp. We live in Colorado and come out all through the winter to use her.
We will be coming back out this coming Wednesday for about 9 days. Hope to head over to Catalina.
I will be back out mid January to do my service. I would love to see your new toy and meet you on one of my trips out.

Big Thanks again,
Stuart
 
I dont know about your alloy mixers but If I thought my cast iron riser could be reliably inspected I would do so.

The trouble is when you open up a cast iron exhaust to take a look you will see an unsightly corroded mess. Cast iron, Seawater, high temperature, and exhaust fumes are one of the most corrosive environments on earth. How exactly do you gauge the results of an inspection? It becomes an excerisize in judging degrees of corrosion.

Yanmar doesnt tell you. They wont touch it for fear of litigation.

Forego the inspection and replace it at 5 years. Flushing I think helps but not a lot. Once seawater is in the grains of the cast iron no amount of flushing will get it out of there.

Have a great time on your trip to Catalina. I am planning a trip to San Miguel. Was at Santa Cruz last weekend.

Bought my Yanmar parts at Anchors Way next to the fuel dock. Nice guys,cheap, and free advice.
 
Gonzo,
Thanks for the tip on Anchors way. It was on my list to find a good parts place in the area. I am close to the bellport yard in channel islands, but have not liked dealing with that place very much.

Not sure how you would judge the corrosion on your elbow. I guess now that it is new you can at least keep an eye on it from here and see what pattern develops.

As far as the alloy mixers go, I am not sure what it all looks like in there till I get in to it. All I know is it is recommended to inspect and clean. For me it is more about curiosity on seeing how it all works. Once I get into it I am sure it will become more clear on what I can do if anything to keep it in good shape.

I love boating around Santa Curz and San Miguel also. I have boating around those islands most of my life.
On my last trip out to Santa Cruz last month the Rangers almost arrested me for having a dog. Boy times have changed out there. So until I can train my dog to do his thing on the boat I am forced to go elsewhere. I just need to be able to spend the time on one of my trip to work with him for a steady week or two.
It was easier to deal with the U.S. Navy getting permission to cross there firing zone along the backside of the islands going by San Nicholas then it was dealing with the park rangers on Santa Cruz. (They were Kevlar vest you know)

As of now the weather does not look to good for next weekend but that is all subject to change at any given moment. A little rain is not a big deal.
Have a good trip over to San Miguel.
Stu
 
Gonzo,
I am a little confused here. Did you say the Yanmar manual calls for the riser to be replaced annually? I cannot find that in any of my manuals for the 3YM30. I cannot find a reference to a riser.

I had a riser on my OMC engine and it was supposed to be replaced every two years. That similar part on my Yanmar engine is called a mixing elbow. The mixing elbow is shown on page 55 of the Yanmar Service Manual. Is the mixing elbow what you were referring to?

In the Yanmar YM Series Operation Manual, on the Periodic Maintenance chart on page 58, is says to "Clean or replace the exhaust / water mixing elbow" every 250 hours or one year, whichever occurs first. Then on page 72, it tells you how to clean the mixing elbow, then it says "Replace the mixing elbow with a new one every 500 hours or 2 years, whichever comes first, even if no damage is found." I don't know why they don't put that on the Periodic Maintenance chart.

Being as the mixing elbow is supposed to be replaced as part of scheduled maintenance, I wonder if Ranger Tugs will start selling the part along with the other scheduled maintenance parts. I wonder if the other Yanmar engines used on the R25/27/29 have a similar scheduled maintenance requirement for their mixing elbows?
 
Yup Yanmars "mixing elbow" is more commonly referred to as an "exhaust riser" around a marina. You have the optional "high rise" or "U type" on the 3YM30 engine fitted in a Ranger 21. They also make an L type.

The larger Yanmars may have the Ltype elbow that you dont have on a 21. The L type mixing elbow doesnt rise at all just points the exhaust down and towards the plastic Vetus thing. The riser type gives you more vertical distance to get the water away from the engine. There isnt enough vertical space in a 21s bilge to use the L type .

The manual is confusing and probably overly cautious because a small team of lawyers was involved in writing it. This part is financially scary for Yanmar. If they say to replace it annually and you dont its your problem.

Its tough to get Yanmar parts anywhere besides the local dealer. They control it very tightly.
 
In the manual for the 4by2 and the 6by2 when it comes to the mixing elbow it just says to refer to your Yanmar dealer. It does not tell you how to inspect or clean. It says the same thing when it comes to the turbo also. I will also be learning how to do that myself. Only because I really enjoy learning to do and doing my own maintenance on my boat.
If anyone has had a dealer check,clean and or replace one of these mixing elbows on a 6by2 or have done it themselves yet then speak up please. In the meantime I will find a yanmar mechanic that will teach me what to look for before I inspect mine this January. If I call enough of them, there is always one that will share the secrets.
I do find it funny that they do not want to share how to do it in the manual for the 4by2 & 6by2. :roll:
 
In the Yanmar BY Service Manual, on page 4-14, it roughly explains how to clean the mixing elbow.

Something interesting. On that same page it says "Anodes are located in the heat exchanger, and the charge air cooler. An additional anode may also be located in the exhaust / water mixing elbow." I never would have guessed anodes would be hidden there.
 
Thanks for that info. I am relying on a pdf on my computer. My manual is on the boat that is 1000 miles away at the moment.
I will look into all this more next week when I get there.

Thanks again, I will look for it on page 4-14

Stu
 
When I had my 110 Yanmar serviced by MER at ~900 hours, they cleaned (by sandblasting) the mixing elbow at that time. I never saw it, but they said it wasn't very bad.

Mac
 
Mac,
Thanks for your input. What you are reporting is about what I would suspect.

I don't feel that I will find much of anything during my inspection mainly because my boat in less then a year old and I keep it in fresh water for part of the year and only in salt when we come out west to use her during the winter. Then a good fresh water flush after each use.

I am learning another thing from you, and that is the sand blasting for cleaning. That is a very easy process. Especially when my wife has a bead blaster in her shop.

Thanks again Mac for a piece to my learning puzzle,

Stu
 
Would the annual inspection replacement be appropriate for exclusive fresh water seasonal usage? We only see a 5 month season.
 
I do not think you have much to worry about being in fresh water. You may want to research that in more detail. It is mainly salt water that will be highly corrosive.
Here is a link that goes into good detail on what happens to engines sitting in salt water.
http://www.oldmarineengine.com/technica ... ion_1.html
 
Thanks Rick!
 
My previous response saying risors on larger Yanmars were alloy was based on what I had overheard. I have not inspected mine yet. If someone can confirm that it would be nice. I would think that one could reasonably inspect an alloy riser as they would tend to degrade with errosion which could be seen. I also would feel uncomfortable just inspecting a cast iron riser used in salt water. As I will soon have 250 hours I will likely inspect mine this year.
 
I wonder if there is any documentation concerning the damage a failure can/will effect. It appears to me that as long as the engine is running, there is no danger of hydraulic lock since the exhaust will push any water out of the manifold and the elbow. If the engine is not running, the same rules would apply as apply to over-cranking. Crank too long without combustion and the water will flow into the manifold but we already know that. It appears to me that if the engine starts, even with a partially plugged elbow, the water should be expelled an no damage result.

It appears to me that the danger is that 1: the elbow cracks and could result in a lot of noise and/or an engine compartment fire; 2: (less likely) the elbow blocks completely and the engine will stall due to backpressure leaving you in need of a tow.

Anyone got any real-world experience here? What am I missing?
 
There is another thread here http://www.tugnuts.com/viewtopic.php?f=2&t=743&p=5202&hilit=exhaust+elbow#p5202 that one of the boats had a defective or cracked exhaust elbow causing his problems. Just saying, that you want all the exhaust out of the engine compartment. I had the water lock or exhaust silencer spring a leak which put water in the engine compartment and bilge. I replaced it right away.
 
What happens when an exhaust riser fails is this:

Everything is fine until you turn off the engine. A slow water leak from the exhaust riser develops from all the corrsion over the years. The water dribbles down your riser into your exhaust pipe. Travels into the engine then finds an open exhaust valve and fills up a cylinder. Upon cranking your engine you hear a bizzare sound of snapping cast iron block. After some rough running you wonder what ever could be wrong. You then arbitrarily pull your dipstick and find white foamy suds.

Back to the launch ramp and new engine time.

I dont think hours on the engine are important here. Mine was only 4 years old and had 100 hours on it. It looked horrible. This is a time driven failure. Seawater soaking with exhaust gasses wil rot through cast iron in time. Frequent running may in fact be beneficial in flushing out the acids that seawater and exhaust create.

Freshwater guys should be watchful. Its not too hard to pulll the exhaust hose and take a look. The rubber tends to vulcanize to the cast iron so it does take some effort to work the hose loose.

Read this link. This fellow has something to say about everyone's riser and says it way better than I do. The Yanmar 3YM30 is basically the sailboat diesel that he refers to.

http://www.yachtsurvey.com/exhaust_risers.htm
 
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