What's in YOUR muffler???

[Stu Jackson]

My son and I just finished replacing the transmission fluid and installing a new heat exchanger bracket on our M25. As we were sitting admiring our work after we cleaned up, and with a toast to his hard work ( !!!), I said: "What's next? Well, this really nice guy on one of the boards has shown us what we need to know about our mufflers. That's next!"

He just smiled...

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Here's a link to a great thread from co.com.  Thanks to Claude for doing the forensics on an old Catalina 34 muffler.

Now you know what's inside!

http://forums.catalina.sailboatowners.com/showthread.php?t=135675

The topic starts with water pumps, but there are two great pictures further down that Claude has posted that are really helpful.

There's also a link to the Catalina Direct muffler replacement page.  http://www.catalinadirect.com/index.cfm?fuseaction=product.display&product_ID=2434

I remember that Ron had changed his muffler out some time ago and wrote a superb report on it.

For C34IA Members, here it is, November 2001 Tech Notes:  http://www.c34.org/mainsheet/pdf/Nov-2001.pdf  (I found it quickly using the "Knowledgebase" xls file.)

[Dave Spencer]

Great information Stu.  Thanks.  I haven't observed any hint of corrosion on the muffler on our 1994 boat.  It has always been in fresh water which I imagine would mitigate the issue.  I assume Claude's C-34 friend is in salt as are you and Ron.  Has anyone heard of a muffler failure resulting in a very messy flooding of the boat?  
Muffler inspection is something I'll put on my "list of things that work fine and should still be good but I better check it and possibly mess it up".  I assume most boat owners have a list like this.  Ron's excellent description of replacing his muffler and his exhaust hoses in the Tech Notes will come in very handy someday.
Here's what my muffler looked like when I had the boat surveyed before we bought it last year.  Some dirt on it and no coolant in the overflow bottle... both fixed now.

[Ron Hill]

Guys : Stu that was a good site with a picture so I can explain a few things :

1. Reason the left inlet is broken off is because of the stiff inflexible hose from the metal exhaust riser to the muffler.  The fix is very simple - the hump hose to take up the engine vibration transmitted thur the metal exhaust riser.  The hump hose absorbs that vibration rather than the inlet tube to the muffler, which you see broke off!!

2. Why the rust?  My best guess is that the stiff WIRE reinforced hose from the riser to the muffler inlet has an interior failure and the wire reinforcing is rusting away!!  Other wise there is no other ferris metal (that I can think of) in the raw water system.  Possibly a non stainless hose clamp? 

A few thoughts

[Stu Jackson]

It has always been in fresh water which I imagine would mitigate the issue.  I assume Claude's C-34 friend is in salt as are you and Ron.  

All I can say is this:

Water corrodes...salt water corrodes absolutely.

The concept that only salt water boats have "issues" is pure fantasy.

It just takes longer (about a week per year, but that's just my guess from reading about it for the last 30 years)...but that has nothing to do with the water, it has to do with the skipper's attention to detail and maintenance.

[Stu Jackson]

1.  Has anyone heard of a muffler failure resulting in a very messy flooding of the boat?  

2.  Here's what my muffler looked like when I had the boat surveyed before we bought it last year.

Dave,

1.  No.  Dirty maybe, but total flooding?  No - 'cuz the way it works is only if the engine is running, right?

2.  OOOPS!!!!  You do NOT seem to have have the hump hose.  That stiff black hose into the inlet of the muffler is exactly what we're trying to point out.  Get a Hump Hose.  Reduce the strain on the inlet port of the muffler.

Like this:  http://c34.org/bbs/index.php/topic,5617.msg35260.html#msg35260  This is a VERY, VERY good discussion of hump hoses and mufflers and exhaust risers.  EVERYONE SHOULD take the time to read the entire thread.

[Ron Hill]

Dave : I also have never heard of a boat flooding either, for the same reason that Stu mentioned.  However, it could make quite a mess and the exhaust smell would be prevalent.
  
That's why I always recommend that people go down below and look at the engine while its running (thru one of the side doors).  I also open the door under the head sink and look at all fittings, especially the raw water strainer.

As far as your boat being in fresh water.  The hull may be, but the muffler and exhaust hoses if full of water that has been aerated with very corrosive exhaust gasses!!   A few thoughts

[Stu Jackson]

Claude has just posted in interesting repair idea.  Click on the pdf file to view.

[2ndwish]

1. Is it possible to add a hump hose without removing the riser?
2. In the fix proposed in the pdf, why not use stainless? Brass won't last long in that environment.

T

[Stu Jackson]

1. Is it possible to add a hump hose without removing the riser?
2. In the fix proposed in the pdf, why not use stainless? Brass won't last long in that environment.

1.  Please read the link in Reply #4.  Yes, I have, because the exhaust riser screws into the flange at the engine end.  I end up with a little blow-by because the threads in the flange are not machined for anything like a "line up" for the horizontal run of the riser to under the head sink.  Even though I used muffler patch paste on the threads, that material has been blown out.  I've never quite understood the "line it up and assemble it all" concept.

2.  Good idea, why not ask Claude at the link I provided?  Please, don't shoot the messenger.

[Ron Hill]

2nd : From many Mainsheet tech articles and posts we have stated you can easily add the hump hose with the riser in place. 

The whole idea of the hump hose is so you NEVER have to go with Claude's fix. 
Even with that fix I'd still recommend that a hump hose installed - as the vertical vibration on any inlet tube (original or fixed) is bound to cause fatigue and eventual failure !!

[scotty]

I've read that stainless is not a good metal for exhaust systems because the chemical composition of exhaust reacts badly with the stainless.

[Dave Spencer]

Stu and Ron,
Thanks for the feedback.  I like the idea of the softer hump hose and will work on that this year.
I hope my comments weren't taken to mean that fresh water sailors get off scott free with maintenance and have no issues... clearly not the case.
I agree that major flooding in case of failure of the muffler seems unlikely to go undetected almost immediately due to the smell and the obvious change in sound one would expect from the engine.  I regularly inspect what I can of the engine immediately after startup and every hour if we are making a passage of more than an hour long under power.  My trusty handheld temperature gauge is useful to monitor the health and consistency of many systems.  I regularly sniff for unusual fuel or exhaust fumes, inspect the Racor and shoot the temp on the stuffing box, exhaust hoses, alternator body and alternator belt from the head access hatches.

[Stu Jackson]

Dave, I agree.

The result of an exhaust riser failure, at least at the nipple, was included in my February 2004 Tech notes report, here for C34IA members:  http://www.c34.org/mainsheet/pdf/Feb_2004.pdf  The billowing black/brown smoke filling the cabin and pouring out of the companionway was a dead giveaway!   [Please note that the article says I didn't use hump hose - I corrected that shortly after the article was published.]

Much the same results would be expected if the inlet or outlet lip of the muffler failed catastrophically.  That, however, doesn't seem to be the case, because the muffler lips tend to fail slowly over time.  What we've learned from Claude's forensics is what the muffler is made of, since most of us simply get to see the white fiberglass cover.

There have been many posts here over the years on rebuilding those lips, because many of us have had leaks where the hoses join the muffler.  Whether or not the steel insert has failed or just the fiberglass surrounding it at, most usually, in the inlet lip, has yet to be determined on my boat.

The very important information from Claude's presentation will be helpful for me in deciding what to do next.

As Ron reported (in the link I provided) both he and Claude decided to remove and replace the muffler, and explained, very well, just how to do it.  Ron also did a presentation on how to replace the exhaust hose from the muffler to the transom.

With all this information, I think all of you now can best assess and determine your own next steps when it comes to that system.

Like folks who still have the old trailer connections and ammeters in their wiring harnesses, I find it interesting that many still have those old solid hoses on the inlets to the muffler instead of the far superior hump hose.  But note, I've had a hump hose on mine since 1998 and have still found major deterioration of the inlet lip.

"Your boat, your muffler"  

[Stu Jackson]

I've read that stainless is not a good metal for exhaust systems because the chemical composition of exhaust reacts badly with the stainless.

Scotty, the Catalina Direct and Catalina Yachts replacement exhaust risers are made of stainless.  Many have reported on making up their own with black steel.  Check the wiki and the Knowledgebase:  http://c34.org/faq-pages/faq-exhaust-pipe.html.  My CY ss exhaust riser has been in since 2003, noted in the report I linked to earlier in this topic.

[Ron Hill]

Scotty : I surely don't know where you read that stainless is not a good metal for exhaust systems ?  What are practically all of the auto mufflers and exhaust pipes made of today?? - stainless!!

I've got a 17 soon to be 18 year old Taurus SW that has the original stainless exhaust system !! I was also the owner of a LTD SW that ate galvanized mufflers every couple of years!!

If you look back in the old Mainsheet tech notes you 'll find that Dave Davis and I attempted to make a survey on the early C34s that had the old iron exhaust risers and the stainless risers.  Most problems with the stainless risers is in the welded joints not the solid pipe.
  
As Stu mentioned that old "black pipe" (like they use in gas lines) was the industry standard of that day until they changed to the longer lasting stainless.

A few thoughts