Mixing Tee Broke Offshore

[Anonymous 121765]

I am posting this as a reminder to all to check the integrity of their systems to avoid this problem.

Last Sunday while coming into John's Pass in Florida; I discovered my mixing tee sheared in two at the threaded connection. Had a friend onboard and kept pumping the bilge w/auto pump & emergency manual pump to get in.

Spring tides were running against us @ 5 knots with me @ full throttle making 1 kt. headway thru the bridge, while water filled the bilge & exhaust filling the cabin. Seems it is always a perfect day's sail right up to the moment something breaks.

I have a 1980 C30 and replaced the 5411 some years ago with the 3M20A. I rebuilt the exhaust w/s.s. threaded fittings and was able to use the orig. mixing tee made of brass.

Two things happened a couple years later. The s.s. exhaust piping because of galvanic corrosion between the fittings and the cast iron exhaust flange, I needed to replace the flange & redid the fittings to galvanized steel. Secondly, the brass exhaust tee gave out. The following chart reveals the different interactions of metals:

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I checked w/RB Groves (Miami), Westerbeke, & Catalina Direct for a replacement. Here is what I found. Because of height restrictions, Catalina custom made the mix tee & you can get a complete piped system for your boat. They asked to have you send your orig. exhaust and they would make a replacement. Unfortunately, it is all s.s. fittings for about $375.00 but I only needed the mix. tee. I tried to get the service rep to give me a number to the manufacturer for just the replacement tee but to no avail.

I asked how they isolated the s.s. piping from the flange and he said they have a putty compound. That was a laugh.

Well that did not work so I made a weldment drawing & I went to my local fab shop that I use. These are great guys and are making me a stainless one for $60.00 & a cheaper priced spare. If some owners have a s.s. system with no problems, that’s a good thing. Additional factors for metal breakdowns are where your boat is located, current draw from nearby boats, etc.

I am posting this for you guys that have issues w/exhaust & mixing tees. If you have a similar problem, contact me and I can send you the drawing. Remember to check your dimensions and make any necessary changes.

Hope this info helps if needed.

CR

 

[Stu Jackson]

Funny how that exhaust elbow always fails only when the engine is running!

Had it happen to me years ago, a one hour motor back to my slip became a four hour sail against the current.

Glad you're safe.

 

[Anonymous 121765]

Stu,
I hear ya pal. Just got back from dismantling part of the exhaust system to remove the mixing tee. Had a scare that I might have drained some water in thru my exhaust. I ran a bypass water line to the bilge and fired up the iron ginney. A little water at first out of the open header but it looked like the normal condensation with a cold engine.

One half of the threads had disintegrated, and the fitting thru vibration had separated away from the 90 deg. ell 2/3's around but didn't separate fully.

The fab shop is making 2 mixing tees as I always have spares for spares. I'm betting you do the same.....
CR

 

[gpd955]

Funny how that exhaust elbow always fails only when the engine is running! .

Luckily mine went while still tied up at the dock. A non-sailor who was going out with me that day said, "It sounds like you left the faucet on." Not something you want to hear on a boat!

 

[Anonymous 121765]

I hear ya jack, not a warm fuzzy feeling. I am having the replacemant made and a spare. Glad you found it while at the dock, sail on.
CR

 

[Windy City]

Are you talking about the T that also contains the thermostat or the T just past the water thruhull with ball valve?

 

[Anonymous 121765]

Windy,

The mixing tee is near the end of your exhaust pipe. I'ts where the water is injected (angled 5/8" aprox. tubing connection) to mix with exhaust and then into your muffler box for pumping overboard. That is, if you have that setup. My 1980 C30 had this setup. Newer boats may have a different configuration pal.
CR

 

[rbmcintire]

Windy, I was just about to ask the same question. Recently, I broke my exhaust tee when I was removing hoses to lift my M-25. Ron, could you send me those drawings? Actually, Would your shop guy consider selling two more?

 

[rbmcintire]

Also, could a dielectric nipple be used to prevent corrosion between the galvanized flange and the stainless exhaust pipe?

 

[Anonymous 121765]

RB,

not a problem. Remember this is for a 1-1/4" exhaust pipe with 5/8" water inlet. My tee is stainless.

Check fab shops in your area. If too expensive my guys can make it and ship it to you.

As I said before, I have height restrictions. Make any dimensional changes if yours is different pal..

CR

 

[Anonymous 121765]

RB,

That could work, but you will need to check the allowable temperature for this fitting in this application. If you look at the galvanic scale in my orig. thread, you will see that galv. steel fittings work well and at a fraction of the cost for stainless.

Let me know what you find out on the fitting..
CR

 

[Twice Around]

FYI - I have a bronze tee just like this for my Atomic 4. I do not know where it came from, but it (and the Vetus water lift) are the only pieces of my exhaust that survived the rebuild a few years back.

CR - I know you are getting stainless built, but you can get a similar bronze unit from Moyer marine, except it accepts 1/2" diameter hose according to their website.

Here is a pic of my hot section dry-fit out from the exhaust rebuild in 2008-2009...threads into 1.25" pipe and 1.62" OD on the other end for 1 5/8" ID exhaust hose. Injection hose is 5/8" - it looks very similar to your diagram. I have some height issues too, as I would expect all C-30 owners to have. I improved upon this design a little bit and added a longer pipe out of the manifold side to provide additional clearance between the mixing tee & water lift..

 

[Anonymous 121765]

Twice,
My orig. tee was brass and lasted for some years but once again, low on the galvanic scale.

I thought it would be easier changing out the galv. exhaust piping instead of having to find a Catalina custom part. Also I don't know if there are differences in the tee's dimensions over the years on their boats.

What was Moyer asking for a replacement?

CR

 

[Twice Around]

I like the SS idea...I was just mostly posting up this as FYI -

Moyer wants $41. long link below which should get you there.
http://www.moyermarine.com/cgi-bin/...all&template=Templates/B000_storebuilder.html

 

[Anonymous 121765]

Shaun,

Thanks for the link. A fitting like that should last for some time.
This will be my third fitting changeout, that's why I went w/Stainless.

There was no outside indication I had a problem went I went out Sunday, But hoping 3 time's the charm.

Thanks for the Moyer info....

CR

 

[Team118]

Hey Ron;

Thanks for the safety alert. Sadly, I'm not sure what you're talking about...

By the looks of the pictures and links, I think you're talking about the pipe that goes from the engine to the water muffler?

Or not... I enclosed a picture of my engine that I took a few years ago during the refab phase. Is what you're talking about in my picture?

Thanks for your help, being as my boat is a '77 and dollars to donuts most of the engine is original, I want to keep an eye out for failures.

Chris

 

[Anonymous 121765]

Chris,

By your picture, your water injection connects to your exhaust manifold (head) not downstream like newer models w/different motors. My water mixing tee is at the end of the exhaust piping right before the muffler box.

I said to Windy that newer boats may have a different configuration. I didn't know what power plant you had, but yea, the water inlet differs from later model/diesel engine configurations.

I see you have a 4 cylinder gas engine. That sure beats my orig. 5411 diesel with <11 HP. The good news for you is that with your current motor, you'll never need the mixing tee...........

CR

 

[Twice Around]

Chris...we have the same motor. Re-check my picture & simply replace my "U" shaped (in build mode, still unwrapped) threaded pipe section with your wrapped section...I had the design like yours that I replaced a few years ago.. the mixing tee is the part downstream of the "wrapped section" where the red hose attaches just before the water lift muffler. My stainless muffler failed long ago, so I have the plastic one now.

Not to bust CR's chops, but the A4 still has a mixing tee. Not sure why he says you'll never need it.

I have more pics if needed.

 

[rbmcintire]

I'm reading that trying to insert a dielectric nipple between the galvanized flange and the stainless exhaust is not feasible nor really necessary for corrosion protection. Diesel exhaust is 1200-1000degF and the dielectric is only rated to 300degF. I took the heat wrap off of the exhaust pipe and saw very obviously that I need new pipe. Good news is I am able to re-use the existing engine flange. OK so, with Ron's galvanic corrosion chart, I am going to redo with HD (orange box ) galvanized fittings and the $40 bronze Moyer mixing tee. This combination is not too bad, corrosion-wise and probably has a reasonable maintenance life-cycle. Guys, I want you to know I am very aware you've saved me a lot of money and quite possibly a very tense offshore situation.

Rob

 

[Old Skool Neil]

We've discussed this at length over on the Moyer site. Note that galvanized pipe is not USCG compliant for engine exhaust hot (dry) sections for safety reasons. At normal exhaust temps the zinc off gasses putting the crew at risk of zinc poisoning.

http://www.moyermarine.com/forums/showthread.php?t=3995