I realize that this question has nothing to do with sailing and for that I apologise......Damon. But over the years I have come to realize that there is a broad spectrum of technicians that are members here and sometimes one has to realize ones limitations, and I have hit a limit. The question has to do with liquid weld, also known as epoxy, better known as JB Weld, can this product be used on a cracked block? The research I have done on the internet gives varied opinions, some swear by JB, some prefer Devcon, others say Belzona.
The specifics of my situation is this, I was given a 19' powerboat, a VIP Victory, with a 4.3L GM motor, motor was not "winterized" and ice cracked the waterjacket. I pulled the heads off thinking that water in the oil could be a head gasket, found the block to be cracked, I want to go ahead and ream out the crack, prep the area properly and fill the crack with JB Weld, I have nothing to loose as the boat was given to me. But I would like to hear from the forum, always willing to learn, after all, if it don't work, can part the boat out.
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Posted: Sep 09, 2011 - 08:30 PM
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Posted: Sep 09, 2011 - 08:45 PM
I doubt it would survive the heat or vibrations, but I must admit I have no specific experience in this application. Have you thought about pulling a block out of a junkyard? That is a common motor and I bet you could pick one up cheap. -
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Posted: Sep 09, 2011 - 10:33 PM
Forget it. We see cracked blocks here every year. People are "going to do it next week end"...nah why pull the boat, it's still like summer.
Then they get busy, a cold front rips through, leaving a clear night, & the temps plunge. Freezing water can exert forces as high as 50,000 psi, something has to give. If you are very lucky it is the frost plug in the engine.
I got lazy when I lived in the North West Territory, temps to -40. I had A Merc IB/OB, BUT it ran antifreeze in the engine, & sea water through a heat exchanger. All I lost was the brass plate on the end of the heat exchanger was pushed out.
JB weld says it can be machined, & it can, so can plastic or wood. Once you crack the block & see water in the oil, the only real fix is a rebuild, or repower. In some cases, depending on where the crack is they can be welded, be aware welding cast iron is tricky. A competent engine facility can give you guidance. If the rest of the engine is low hours, a rebuild, using most of your components may be the best route. You may be able to find a mid to high hour engine from a wrecked boat. You cannot just go to a junkyard, find a block from a wrecked engine & swap components. Your pistons will not just go into another block, nor can you swap the crank & camshaft without machining. Heads can be swapped,(after milling), but that is not your problem.
You willhave to do some research & decide if the package you end up with is worth the investment to properly fix the engine. In my younger day we rebuilt quite a few big block engines & small block GM engines, you can do it really cheap, or you can do it right. JB Weld epoxy for a cracked block is neither.
PS Damon is at Jaunas, it might slide by him, the drunk fest is tonight.
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Posted: Sep 09, 2011 - 11:06 PM
I used JB Weld on my walk-behind mower, oil drain plug was overtightened and split the case, V'd out the split, cleaned area with acetone, keyed surrounding area with rough sandpaper, applied JB Weld, that was 6 months ago, still no leaks.
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Posted: Sep 10, 2011 - 05:30 AM
You didn't really describe where the crack is. Assuming that you saw it after pulling the heads it must be
in the block deck. If that is the case it won't likely hold with an epoxy. The stress alone from torquing the
head bolts will probably crack the epoxy. With that said, I have repaired several external water jacket
leaks using Belzona and Mega Metal. Both of these are expensive but far superior to JB weld. If you are
up for a project and want to keep it cheap, then a junk yard block is the way to go. Another consideration
is what else may have cracked. possibly the marine exhaust manifolds?
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Posted: Sep 10, 2011 - 11:12 AM
could be a lot of time spent on repairs that don't hold, new gasket kits, etc.,. call your local ace engine rebuild man and or bring it to him. a few bucks spent on a professional opinion is well worth it. not only that, motorboats are full of money pits, trim pumps, wire harnesses, crud in tanks, rotten floors, and don't forget the drama of motors themselves...a free boat turns into several thousand K real quick. my buddy is still restoring his chris craft, he is 2000$ in this season, been out twice, still needs more$$$, i have sailed 20 times. it's always "i just need...." or "the boats running good except for...". gas ain't getting cheaper! good luck!
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Posted: Sep 10, 2011 - 01:05 PM
I have used JB weld to repair a cracked case on an aluminum dirt bike engine, it worked well enough for that.
Real problem I see in here is that you have water in the oil, its not as simple as a cracked water jacket. The ice must have pushed the head up and possibly distorted it, which lead you to thinking you had head gasket problems.
If I was you I would search car-parts.com and find a 4.3 out of a truck or van, you should be able to get a long block for $300 or less. Pull your motor and install that one with your marine componets.
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Posted: Sep 10, 2011 - 02:08 PM
I hear you guys, but I have just finished repairing the crack, drilled "stich" holes along the length of the crack, went all the way through the casing into the waterjacket, used dremel to ream out crack, worked awesome, keyed a large area around the crack, cleaned area using acetone, pulled a vacuum on the waterjacket using a wet & dry, it sucked the JB Weld into the stitch holes, filled the crack with JB Weld, smoothed JB out using good old "spit on finger" method. The crack ran parallel to the head, up and over a divit on the block, effectively sneaking under the head gasket just a fraction, I epoxied the whole lot, head and all, will sand JB down when cured, hoping the head gasket will seal area when I put it all together.
The leak was very small, water in the oil after a day on the lake, if it fails I'm out of pocket $136 for all gaskets, will recoup that if/when I part boat out, if it holds, well and good, if it don't, I learned a lot, 1st time I pulled heads on a motor.
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Posted: Sep 10, 2011 - 10:21 PM
Good for you, sometimes you just have to say WTF, spend a few $$, & if it's a bust, well maybe learned something.
If you have not done the reassembly yet, DON"T HURRY. This is one job that a little knowledge is a dangerous thing. Spend some time researching the installation of heads, there is more to it than just twisting some bolts.
Beg, borrow, or steal an accurate torque wrench. Find out the pattern in which the bolts are tightened. Read the procedure 4 times, you might discover something, seriously. Even the head gasket may have right/wrong side. A few month ago my sailing buddy & I did a major on his 4WD, water in the oil. It turned out the head was cracked. We sourced a set of rebuilt heads cheap. Upon assembly we found there was an upside, & a downside to the head gasket. Who'd have thunk, the damned thing was identical, other than some colored markings on one side. We only noticed it upon the second read of the shop manual.
Those areas between bosses, valves, or "divots" are where stresses concentrate, & are the most common areas to find cracks.
You may have to mill the heads to ensure a totally flat surface. They may be warped a tiny bit from heat. It sounds logical to expect the gaskets to absorb some imperfections, but small out of tolerances can lead to premature gasket failure. Avoid the instinct to get twisting wrenches, the more research you do before your first try will be worth way more than the $136.
I hope your experiment works, but what is worse is the engine is a bust, but the fail was caused by some seemingly small step that was omitted. This will bias your thinking on any further projects, perhaps you conclude it is never worth the time/money, when in fact one small step in the assembly was the fatal flaw. There is lots of good info on engine assembly available. Read all you can find, then you know you gave it a fair chance to be successful.
Post how it holds up.
Edited by Edchris177 on Sep 10, 2011 - 10:24 PM.
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Posted: Sep 11, 2011 - 07:41 PM
Heads are back from being inspected, no need to be surfaced, have sketches of torque pattern as well as the torque specs, heads have been cleaned up as well as intake manifold, just waiting on gaskets, know about the gasket "which side is up" problem, will have to contact supplier for that info if necessary. Having done some research on sterndrives has made me realize just how many things can go wrong with powerboats, makes me so much more appreciative of my P18, so what if it takes 45 min to setup to go sailing as compared with 2 min to put a powerboat in the water, at least I get to sail 1ce a week.
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Posted: Sep 12, 2011 - 05:47 PM
Clean everything really well, & find out what bolts require Loctite, & which ones don't. Usually it is Loctite "blue", that can be removed, the "red" needs heat to break the grip.
You may find it difficult to keep gaskets in place while setting manifolds into position. Much depends on the engine, V-6, Straight 6 etc. You can use a gasket goo.
As a young whisker, back in Alberta, on my buddies ranch, we were always tearing down & rebuilding stuff. His Dad was mechanic in WWII, & had a full machine shop, big enough for tractors & combines. He showed us a lot of lo tech solutions. One was to use thin sewing thread to tie the gaskets in place, a loop through 4-5 bolt holes. The thread will compress to nothing, & serves to prevent the gasket from falling out of place as you lower the manifolds into place.
I really hope to be proven wrong, I have serious doubts about JB to hold in this application. I've used it numerous times, but never where pressure is involved. the water jacket will be pressurized once the engine is at temperature.
Let us know how things turn out.
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Posted: Sep 12, 2011 - 08:39 PM
Marine engines have 2 types of cooling systems, 1) a closed cooling system which as the name implies, works under pressure, and a 2) a raw water system, also known as seawater system which draws water in from outside the boat, circulates it and then spits it back out. My decision to go with JB Weld was based on the fact that this boat has the raw water cooling system, it is not pressurized. I filled the crack as above, then drilled 2 rows of anchor holes on either side of the crack angling slightly in towards the crack, I layered JB weld over the initial fix, anchoring it into the holes, I'm pretty confident this fix will hold. Gaskets arrived today but will only be able to install them on the week-end, gives the JB Weld more time to cure....
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