High temp epoxies to fix crack

[Honeyman]

So the water/exhaust leak on my 3GM30 Yanmar is due to a cracked exhaust elbow that apparently was damaged at Hunter during assembly in 1994, hastily (and poorly) welded up and stuck in the boat anyway. Thats the only explanation to what I found when I cut an access panel into the aft bulkhead between engine and aft cabin. My real question is, has anyone used a high temperature epoxy to fix a crack in an exhaust elbow? Other than the crack, the elbow is fine and not ready for replacement...very low hour motor.

 

[KD3PC]

jb weld and similar products would likely do better than epoxy...check with or call Jeg's or Summit Racing...they make some stuff to do exactly what you are talking about. One of the guys at our drag strip put it on temporarily, and that was 3 years ago..

Best of luck

 

[zeehag]

j-b weld comes to mined---lol -- lookslikei am not the first one to think like this--- goood luck...

 

[Steve C.]

I don't think trying to repair it is a good idea. Exhaust fumes will still leak out unless it is welded or replaced.

 

[Billbeard]

I’m not positive about this but Jb Weld and Marine Tex are both OK for some hot fix’s but I don’t think cast Iron is one of them at least not for exhaust leaks the cast iron is used because of all the expansion and contraction the epoxy will expand and contract at a different rate then the iron and will crack and separate from the metal . I believe the only way to fix a manifold is to preheat the iron before welding and not a few welders shy away from this work it is more an art then science.

 

[navigator97]

If it were me, I'd just replace the mixing elbow.. They are usuall good for about 5 years or 500 hours, and then they are pretty 'coked' up and restrict the passage of exhaust gases and cause back pressure making the diesel unhappy. You say it's a '94' (thats 16 years), how many enginr hours on it? Just my 2 cents worth.

Dick, S/V Puffin 1990 H-33.5

 

[rardiH36]

It's Probably a Gonner

My take is that your elbow is caput .. successful repair is unlikely. Maybe the epoxy will work to get you into the next port... but not much more.

Last year, I noticed a slight crack in the elbow for my Yanmar 2QM20. Fortunately I quickly found an exact replacement that was reasonably priced since it had been in the vendor's inventory for quite a few years and it was still on his books at his original price.

But see the attached pictures below of what my cracked elbow looks like today. After taking it off, I considered maybe an epoxy job or find somebody to weld. First, I drilled holes at the end of each crack to relieve the pressure, and then I reamed the crack out so the epoxy (or professional weld) would fill in. Then I just put it on a shelf in my garage. What has happened in the year that the elbow has been off my boat, and I guess has dried out from imbedded moisture in various cavities, is that the existing cracks have gotten bigger and its delaminating in rust bands. And a new crack has formed all by itself. When I pick it up and slap it with the palm of my hand, rust cascades out. Definitely not repairable.

Here's a link to a thread a couple of weeks ago that might give you some assistance as well?

http://forums.sbo.sailboatowners.com/showthread.php?p=729522&highlight=elbow

 

[packman]

Cracked cast iron is repairable, but it takes a specialist to do the job, most cast iron welds crack right next to the repair in fairly short order without very careful preparation, preheating and cooling protocols. Unless it's a rare or unobtainable part, the smart money is on replacing it. Taking chances with an exhaust leak inside your boat is asking for it