Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canidate?

[jacoblh13]

I have a Mercruiser 3.0 Litre with a cracked block. The crack is 7 inches approximately and is directly below the exhaust manifold. The engine runs fine, doesn't get hot and I have no water in the oil. I ran the boat Saturday with no trouble. I thought I just had a bad gasket but turned out to be a crack.

I know JB weld is not the "proper" fix, however I am curious if this is a good candidate to try it on?

So i guess my question is: Is the location of this crack something that might be fixable by JB Weld? Please see the pictures below. Thanks in advance for any and all help!

 

[CobiaXL]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

Use a grinder to roughen it up the crack,Drill a hole in each end of crack and smear some epoxy on it.Go boating and just keep a eye for any leaks,if so smear some more epoxy on it.Seen it work and last longer then the engine did.

 

[jacoblh13]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

So how far do you drill a hole? Also should I apply it in thin multiple layers or try one good coat?

Thanks!

 

[Saqbcq]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

You can do that but a permanent fix would be better,clean it with a die grinder and have it welded. Auto shop or metal shop has a welder always readily available. Disconnect your battery and unplug your alternator first. Good luck

 

[jacoblh13]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

How does this look as far as preparing the block and cleaning it? I also drilled two indentions on each end. I guess this is what people mean when they say drill a hole??

 

[Pete104]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

Blow it out with compressed air, hit it with some acetone. And start shmooing. Try to push some into the crack, then just smear some.

 

[CobiaXL]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

Looks good...Apply 2 coats.Feather 2nd coat further out then 1st coat. Wouldn't hurt to rough up first coat before applying 2nd coat.

 

[fibersport]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

You have to drill a hole, not just an indentation. The reason for the hole is to stop the crack from growing. What you will get is water inside the crack, it will then cause the cast iron to rust and the rust will cause the crack to be pushed apart which will then cause the crack to continue. The block should only be about 1/8" thick I think so don't go crazy and drill a 4" deep hole, just enough to punch through the outer water jacket. You'll know when you've gone through it. Then clean out the rust in the crack, all the way through will give you the best chance of having the repair last - as was posted before, grind the crack open to clean it out. A small carbide burr in a dremel would work, a die grinder would be better, although you don't want to open the crack too much, just enough to clean out the rust. Welding cast iron is kind of tough, you need to pre and post heat the surrounding area to prevent the metal from getting harder and cracking later. Sometimes the weld will work, others it won't. Looking at your pictures, if you remove the core plug and can get some epoxy INSIDE the water jacket to help seal the crack, you would really stand a good chance of the repair lasting.

 

[boatman321]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

Ran into the same issue and looking for options short of replacing the motor. Can you give us an update on the fix. Did your application of JB Weld fix the problem at least for the time being?

 

[jacoblh13]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

I made the repair using JB Weld. So far so good! I have taken it out twice and ran it for about an hour each time. No leaks.

I will continue to watch it. I was hesitant to make the crack any larger.... so I didn?t. The crack was actually quite open and was angled up towards me. I just cleaned the heck out of it. The angle of the crack made it easy to get the JB Weld into the crack.... since the JB Weld wanted to run a tad it help that it cracked up instead of down. I am going to monitor the area and hopefully this repair will last several years.

 

[CobiaXL]

Re: Merc 3.0L with cracked block below exhaust manifold, is this a good JB Weld canid

Ran into the same issue and looking for options short of replacing the motor. Can you give us an update on the fix. Did your application of JB Weld fix the problem at least for the time being?

The fix works but is temporary,Could work for the life of the boat but could also blow out today.Make sure your bilge pump works every time out,and check the backup bilge pump too.Fail to prepare,prepare to fail.