How long will a JB Weld job on a cracked block last

[itsmetibbs]

I picked up this boat for $300, so it doesn't really matter if the job lasts a long time. I was just wondering if anyone's had experience fixing a cracked block with JB Weld. My experience thus far (5 hours) is that it is holding well enough. Below is a video of me filling the cracks and running the boat on the lake to test it.

https://youtu.be/54Y6o4aC1u8

 

[ondarvr]

It could last 10 minutes or 10 years.

 

[Rick Stephens]

I put a push rod through the side of a Cat 3406 block, patched it up with JB and it lasted another 500,000 miles, who knows how many miles after I sold it. If it never comes under pressure, it can last nearly indefinitely. Add a little pressure, or rusting under the resin, and it may fall apart rather soon.

 

[Dave-R]

I repaired a 4.3 block that was cracked on both sides of the water jacket 5 years ago, and they have both held up fine. I would have taken the exhaust manifolds to a welder and have them brazed. I think they will get to hot for the JB weld. Dave-R

 

[HT32BSX115]

Also, pay close attention to your engine oil. If it turns milky or gray, you probably have internal cracks. It's not possible to fix those. In addition, if your engine hydrolocks after a shutdown, you probably have internal cracks in the exhaust manifolds. It's also not possible to fix that either.

If you only have small leaks on the exterior of the manifolds and block, and it's just a "drip" or tiny stream, you could probably run that way for years. (I'd get a good bilge pump though)

If it's a nice boat, I would get a truck 350 from your favorite wrecking yard, and a new center-riser exhaust kit.... You would have a reliable good running boat for years to come!

I would have taken the exhaust manifolds to a welder and have them brazed.

That almost never works. It's VERY hard to keep brazed or welded manifolds from cracking again and you cannot do anything for the inside.

 

[stonyloam]

That looks pretty good, but on a crack as large that I would add a layer of fiberglass to reinforce the JB. Just check it every time you go out, could last the life of the boat. Just don't let it freeze again