4.3 cobra crack

[royf]

Hi, i am new to the forum and to boating. I bought a 1994 Seaswirl that I thought needed exhaust manifolds. When the mechanic pulled the manifolds he called me and said there is a small crack in the block!! My first thought is to junk the motor right now, but he is telling me the engine cylinders are all at 180, and to consider a repair. Any body had this experience and could give me your advice??

Roy

 

[Maclin]

Re: 4.3 cobra crack

Welcome.

We would need more background on why you thought it needed exhaust manifolds. Have you had this boat running yet? What does the oil look like on the dipstick? Also where the crack is, on the side of the block, or on the head between ports, etc. Pics are always good.

If the crack runs fron to rear on the side of the block it may be repairable from the outside. But there may be cracks on the inside from the cooling passages having frozen solid and expanding, and those would not show up (without dissassembly and inspection) until the engine has been running a while and water leaks from cooling passages into the oil pan, rapidly overfilling. In that case you will need at minimum a new block.

 

[royf]

Re: 4.3 cobra crack

Welcome.

We would need more background on why you thought it needed exhaust manifolds. Have you had this boat running yet? What does the oil look like on the dipstick? Also where the crack is, on the side of the block, or on the head between ports, etc. Pics are always good.

If the crack runs fron to rear on the side of the block it may be repairable from the outside. But there may be cracks on the inside from the cooling passages having frozen solid and expanding, and those would not show up (without dissassembly and inspection) until the engine has been running a while and water leaks from cooling passages into the oil pan, rapidly overfilling. In that case you will need at minimum a new block.

Hey, thanks for responding so fast. I did take it out for about two hours and it ran pretty good. I noticed a crack along the top of the exhaust manifold when I got it home and then looked at the under side of the manifolds and could see cracks along them. At the shop I explained what i saw to the mechanic and later he found about a three or four inch crack above the middle spark plug hole about half inch below the head gasket.

The oil is perfect, the fresh water anti-freeze is worn looking but not oily. Like i said the mechanic told me all six cylinders are at either 160 or 180(i cant remember, but they match).

I hate to throw Good money after bad. But if there is a common prven way to repair then I would much rather spend the money on fuel.

 

[royf]

Re: 4.3 cobra crack

The boat isnt at my house so I can add any pictures.

 

[Bondo]

Re: 4.3 cobra crack

Ayuh,.... Welcome Aboard,.... If the cracks are to the Outside of the motor, just epoxy 'em up, 'n run it til she pukes,...

If there's cracks goin' into the oil, ya need a new block,....

 

[Maclin]

Re: 4.3 cobra crack

If the oil level is not rising and the oil looks ok after a hard run then it seems you are lucky enough to just have cracks on the outside.

The spark plugs are in the head, so not sure exactly what this means ...
"crack above the middle spark plug hole about half inch below the head gasket"

I am sure the mechanic knows what he is looking at, but definitely new manifolds were needed and he is right to want to seal the crack(s) in the block.

You can search for engine block crack fixing, basically drill small holes on each end then epoxy as Bondo referenced. Hopefully your mechanic is aware of the proper methods.

Good luck on this project!

 

[ChrisSchumacher]

Re: 4.3 cobra crack

Hi, i am new to the forum and to boating. I bought a 1994 Seaswirl that I thought needed exhaust manifolds. When the mechanic pulled the manifolds he called me and said there is a small crack in the block!! My first thought is to junk the motor right now, but he is telling me the engine cylinders are all at 160, and to concider a repair. Any body had this experiance and could give me your advice??

Roy

I had the same problem in the same spot. I cleaned the crack as best as I could. Then I used "Loctite Primer T" to clean the crack. Then I filled the crack with "Loctite 290". 290 is a "wicking" Loctite. I runs into the crack and hardens up to a plastic sealing the crack. Good to about 300 degrees F.
Fixed my boat 10 years ago, still running fine!!!! No sign of water at all in the area of the crack.

 

[royf]

Re: 4.3 cobra crack

How did you come up with Locktite for a repair, isnt it usually for threads??

 

[ChrisSchumacher]

Re: 4.3 cobra crack

Loctite 290 Wicking Grade MIL-SPEC Medium-High Strength Green Threadlocker

Top Pick Loctite? 290? Wicking Grade MIL-SPEC Medium-High Strength Green Threadlocker is a medium strength wicking threadlocker for pre-assembled bolts up to 1/2" (12 mm). Penetrates threads by capillary action. Secures set screws and other assemblies after settings are completed. Seals welds and porous metal parts. Mil Spec: Mil-S-46163A Type III Grade R. NSF/ANSI 61 Certified. Applications include instrumentation screws, electrical connectors and set screws and also seals porosities in welds and metal parts. Mil Spec (S-46163A) Type II, Grade M. NSF P1 Certified.

Loctite? 290

Website Link.

 

[ChrisSchumacher]

Re: 4.3 cobra crack

290 is used for threadlocking on bolts and nuts already assembled. Because of its "wicking" action is penetrates the crack deep into the metal. Once inside it cures because of the absence of air. If you purchase Loctite you will see the bottles come half full. If the bottles were full it would harden. ANYWAY, once in the crack it hardens into a plastic and is good for around 300 degrees F. Since there is really no pressure in the water jacket and the engine never gets up to 300, your good to go.

I just posted a description of 290 and a link to their web site for the product.

 

[ChrisSchumacher]

Re: 4.3 cobra crack

Good to 250 C or 480 degrees F. From the spec sheet.

 

[HT32BSX115]

Re: 4.3 cobra crack

Good to 250 C or 480 degrees F. From the spec sheet.

You could try it.

Let us know how it works........Otherwise, grind the exterior of the crack and use a GOOD epoxy (like JB Weld)

Even a small leak isn't going to hurt anything (you do have a bilge pump?)

You're biggest problem with block cracks is going to be the internal ones. (V-8's/V-6's almost ALWAYS crack "in the valley" right next to the push-rods directly above the tappets)

After you get the new manifolds on, run it on the lake at normal cruising speeds long enough to get the engine completely up to normal operating temp.

Check the oil frequently. If it gets higher and/or turns grey/milk-shake etc, plan on getting another engine.

 

[royf]

Re: 4.3 cobra crack

You could try it.

Let us know how it works........Otherwise, grind the exterior of the crack and use a GOOD epoxy (like JB Weld)

Even a small leak isn't going to hurt anything (you do have a bilge pump?)

You're biggest problem with block cracks is going to be the internal ones. (V-8's/V-6's almost ALWAYS crack "in the valley" right next to the push-rods directly above the tappets)

After you get the new manifolds on, run it on the lake at normal cruising speeds long enough to get the engine completely up to normal operating temp.

Check the oil frequently. If it gets higher and/or turns grey/milk-shake etc, plan on getting another engine.

Yep thats the plan now. Its getting fluids changed and tune up kit since its apart. mechanic is also changing out the bilge pump wiring which is hokey looking. Where do you guys buy the manifolds??

 

[HT32BSX115]

Re: 4.3 cobra crack

Oh! You were talking about an OMC 4.3L engine in your PM...........:faint2:

I am not sure you're going to find manifolds for that engine around here locally! If they're 'bat-wings' they're not going to be cheap nor should you use them anyway.... (some swear by them though)

You're going to need to find an online supplier and possibly switch to manifold/riser combinations.

I am not sure you can even buy those single piece manifolds anymore.


There are stainless steel (single-piece) models available but they'll probably cost more than you could sell the boat for