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Old 05-23-2012, 06:23 PM
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Prostarski190 Prostarski190 is offline
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Cracked engine block

Has anyone ever used JB Weld or Marine-Tex on an exterior engine block crack? If so did it work, what was your experience, and would you recommend either or?
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Old 05-23-2012, 08:25 PM
waterlogged882 waterlogged882 is offline
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Old 05-23-2012, 08:32 PM
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Old 05-23-2012, 08:34 PM
mdskier mdskier is offline
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I bought a boat (not Mastercraft) about 12 years ago. After 2 years of very casual use (total of about 4 weeks a year) the engine failed. The mechanic that replaced it said the block had Jb Weld on it covering a crack.

So I agree with Cloaked, fix it right the first time. The JB Weld might hold up for a little while (or it might not).
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Old 05-23-2012, 08:49 PM
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Double D Double D is offline
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My brother in law used it on a Merc 305 I/O for a few years. Kept having to reapply it until he rebuilt it.

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Old 05-23-2012, 08:51 PM
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Spork Spork is offline
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yes the crack can be welded and fixed, the cost will largely be associated with how much work you put in it, the welder won't do it in the boat, if you find a welder that says he can do it in the boat you need to find another guy to do it as this guy doesn't know what he's doing, the repaired area needs to be heated before the welding begins, and the engine will need to be taken apart so you'll either have to pay him to prep it or you remove and prep it yourself. I personally have had several blocks repaired this way, take it apart and sent it to a race shop.

Last edited by Spork; 05-23-2012 at 08:54 PM.
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Old 05-23-2012, 09:01 PM
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ahhudgins ahhudgins is offline
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I actually brought a trick ski home this week in order to repair a hole with JB Weld!

Repair a cheap trick ski? Yes.
Repair a cracked block? No.
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Old 05-23-2012, 10:31 PM
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I want to thank everyone who has taken the time to reply and offer their opinion. I do value the wealth of knowledge available here. I'm still weighing my options and gathering information.
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Old 05-24-2012, 05:47 AM
ctjahn ctjahn is offline
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JB Weld

I feel it is complete crap and should never be used but.... that being said.... I aways carry it in the toolbox for emergency repairs.

I did use it on a race engine for a season. As previously stated it is a temporary fix and should never be considered perminent. Also agree it is all in how it is applied. I stripped the paint, degreased, used brake clean (no water in the block), heated the surface and spread it wide around the crack I had....

I have a very good welder contact who can weld cast iron but I didnt want to warp the block or heads mid season. (The process uses a LOT of heat to properly weld and penetrate).

After the season was done it was properly fixed with a weld, block and head were decked and pressure tested. It was an SOB to get off...(the JB). I needed to use an angle grinder to remove it.

Your mileage may vary.
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Old 05-24-2012, 08:42 AM
Ironhorse Ironhorse is offline
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I used it once on a Raptor engine and got stuck in the hills when I lost 90% of my engine oil out the same crack. DO NOT USE THIS ON YOUR ENGINE. There is far too much risk of ruining a great day and leaving you stranded. Sorry to hear about your engine and good luck.
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350, block, cracked, engine, lt1

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