engine exhaust to muffler failure (atomic 4)

steven

Sustaining Member
Adventure yesterday bringing her back from the yard (new bottom paint).

Doing 6.1kts at 2100rpm.
Lost power suddenly.
But the engine re-started, revved fine in neutral; then stalled in fwd.

So killed it and sailed home.

On inspection found this (see pictures - pic2 is contrast enhanced so easier to see the failure):
- pipe at the top comes from the engine exhaust manifold.
- hose in the upper left goes to an outside vent.
- hose coupled below goes to a water lift muffler.

You can see that the Y pipe has come loose at the top.

The failure was pretty messy.
Light grey smoke from the lazarette - I assume exhaust escaping from the break
Water - fresh not mixed with oil or gas - dripping from everywhere in the engine area. I assume from the muffler absent exhaust pressure to push it out the tailpipe.

So now what ? I'm thinking the coupler threads rusted out (its 12 years old) and it should be replaced.
Hoping the top pipe threaded female side is ok.
Anyone know who makes one ?
1 1/2 inch OD. The vent leg is 7/8" OD.

This is all new to me. Any advice is very welcome.

1631218943418.jpegexhaust coupler IMG_1631 enhanced.jpg



--Steve
 

bigd14

Sustaining Member
Blogs Author
Hi Steve, that sounds stressful!

In your photo, shouldn't the hose in the top left be the raw water injection back into the exhaust? It's running to an outside vent? That seems unusual. Or maybe that hose is not showing in these photos? I have a system where there is a tee before the raw water is injected into the exhaust which leads to a small diameter hose to a stern thru hull (second photo). This is to create a siphon break. Water pees out of this hose in addition to the normal flow from the exhaust hose during engine operations.

Is there any chance that water got back up into the engine and caused it do die? If so, this would require immediate attention to get it out and save the engine.

A metal fabrication shop could probably make this raw water/exhaust mixing pipe setup for you pretty inexpensively. You could also replace it with a mixing elbow (first photo). But you might have to rework hoses and fittings from the exhaust manifold. This would be a good time to examine all the hoses back there and replace any suspect ones.
 

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bigd14

Sustaining Member
Blogs Author
Thought I would throw in a photo of the rest of the exhaust system, FYI.
 

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Kenneth K

Contributing Partner
Blogs Author
Unless Atomic exhausts are vastly different from diesels, the cracked part is the "mixing" or "injection" elbow, where cooling water (the hose from the left, as bigd14 said) is injected into the hot exhaust pipe.

Rather than coming loose, I'd say the elbow threads rusted through and cracked, likely leaving thread fragments in the adjacent pipe piece above. In any case, with rust-through like that, all the piping should be replaced clear back to the engine exhaust flange. You can replace it with 316 stainless pipe.

Search online for "1.5 in exhaust elbow" and much will appear.

Screenshot_20210909-200521.png

Or, Moyer Marine may sell something similar, specifically for the Atomics.
 
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steven

Sustaining Member
". . . shouldn't the hose in the top left be the raw water injection back into the exhaust . . ."
Yes that is correct. It is goes to a vented loop to water from the engine.

Moyer Marine
Talked with Don Moyer. He has a exhaust hot leg exhaust riser + elbow assembly made for a Catalina 27.
Looks like it will fit.

He also has a bronze mixing elbow that seems like it would work, but the existing hot legs looks like it has the threads are damaged where the elbow rusted/broke off. Since I have to remove the whole leg on the chance it can be fixed, I figure I might as well replace.

Any tricks for getting the rubber hoses off ?
They are in good shape so I can reuse if I don't have to cut them off.
Clamped on very tight.

-------------------
". . . that sounds stressful!"
My creek is entered through a 1/4 mile of serpentine channel 6 foot deep 12 feet wide (= 1/3 boat length) - with 2 ft of water on both sides - so it is essentially a ditch.
I lost power just as I turned into the channel.
Fortunately I was heading north-ish and the wind was south-ish. So only needed to unfurl the jib.
If the wind had been northerly I would probably have been driven aground.

After another 1/4 mile reach in the creek.
Turned into my slip deadstick (except for about 1 foot of jib unfurled to help steer.)

Could have been alot worse.

--------------------

thanks
--Steve
 

Kenneth K

Contributing Partner
Blogs Author
Any tricks for getting the rubber hoses off ?

Old hoses form a tight bond with the fitting and often cant be "pulled" off because pulling just causes the hose to constrict and clamp tighter.

Instead, push on both sides of the hose (the cut end and the long end) to "enlarge" the hose to break the bond. Then you can pull and rotate the hose to remove it.
 

Gary Holford

Member II
". . . shouldn't the hose in the top left be the raw water injection back into the exhaust . . ."
Yes that is correct. It is goes to a vented loop to water from the engine.

Moyer Marine
Talked with Don Moyer. He has a exhaust hot leg exhaust riser + elbow assembly made for a Catalina 27.
Looks like it will fit.

He also has a bronze mixing elbow that seems like it would work, but the existing hot legs looks like it has the threads are damaged where the elbow rusted/broke off. Since I have to remove the whole leg on the chance it can be fixed, I figure I might as well replace.

Any tricks for getting the rubber hoses off ?
They are in good shape so I can reuse if I don't have to cut them off.
Clamped on very tight.

-------------------
". . . that sounds stressful!"
My creek is entered through a 1/4 mile of serpentine channel 6 foot deep 12 feet wide (= 1/3 boat length) - with 2 ft of water on both sides - so it is essentially a ditch.
I lost power just as I turned into the channel.
Fortunately I was heading north-ish and the wind was south-ish. So only needed to unfurl the jib.
If the wind had been northerly I would probably have been driven aground.

After another 1/4 mile reach in the creek.
Turned into my slip deadstick (except for about 1 foot of jib unfurled to help steer.)

Could have been alot worse.

--------------------

thanks
--Steve
Heat guns work good for loosening hoses. A few years back I rebuilt my exhaust system with the help of a pipefitter friend with black iron pipe. I cruise fresh water so maybe not applicable in salt?
 
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