View Poll Results: Marine Tex or JB Weld for the crack

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  • Marine TEx

    5 29.41%
  • JB Weld

    12 70.59%
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Results 1 to 18 of 18
  1. #1
    Cadet
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    Default Marine Tex Or Jb Weld

    Ok, the 3.0 is cracked. External crack only. Should I use Marine Tex or JB. There is alot more experience on this board than I have. Thanks.

  2. #2
    Master Chief Petty Officer
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    Default Re: Marine Tex Or Jb Weld

    I would say JB just because it seems to work for other people.
    Either way, its just a temporary band aid to mask a big problem.

  3. #3
    Lieutenant Junior Grade danond's Avatar
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    Default Re: Marine Tex Or Jb Weld

    You forgot the 3rd option - "replace engine block".
    1989 Starcraft 171S Select "Cap'n Crunch" / OMC Cobra 4.3 V6 / 432APRMED

    If you're going to keep that OMC Cobra, please for the love of everything good in the world, get an OMC factory service manual. Not a Clymers, Not a SELOC. You can find them on eBay.

    My boat repair website: http://transomfix.dcpolk.com


  4. #4
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    Default Re: Marine Tex Or Jb Weld

    Not worried about replacing the engine this summer. As long as the temp fix can last me through the season. Long block in the fall when the boat is out for the season.

  5. #5
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    Default Re: Marine Tex Or Jb Weld

    Just found out some interesting info. JB Weld is good to 500 degrees, while Marine Tex is good up to 250°F constant temperature in a dry environment, with spikes up to 300-325°F.

    Guess there is my answer.

  6. #6

    Default Re: Marine Tex Or Jb Weld

    Sir...do yourself, your family, and any friends a favor, and change the motor. Getting stuck out on the water sucks..and can ruin a whole weekend. You gotta take the motor out sooner or later anyways, and its still early in the season. You'll be happy you did it the right way. You said in an earlier post that this site has the most experienced people around. Listen to what we/they tell you to do. Your going at this with blinders on sir.
    Never be afraid to try something new. Remember, an amateur built the ARK, a large group of professionals built the TITANIC.


    1997 33' Scarab Thunder...twin 502's


    1965 GTO "street car"
    565 ci Pontiac..2 stages of sauce
    1400 hp on a fat tune

  7. #7
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    Default Re: Marine Tex Or Jb Weld

    Quote Originally Posted by tinman565 View Post
    Sir...do yourself, your family, and any friends a favor, and change the motor. Getting stuck out on the water sucks..and can ruin a whole weekend. You gotta take the motor out sooner or later anyways, and its still early in the season. You'll be happy you did it the right way. You said in an earlier post that this site has the most experienced people around. Listen to what we/they tell you to do. Your going at this with blinders on sir.
    I do appreciate the concern. But the funds aren't available for a $4-5000 repair now. 25 hours is the average for my boat in the summer. The crack is fairly small, and JB weld hopefully will do the trick. Again, thanks.

  8. #8
    Seaman Peaceful Pirate's Avatar
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    Default Re: Marine Tex Or Jb Weld

    Sometimes we can get caught between not being able to do the “right and best” thing and wanting to do something!

    Go with JB. The crack is most likely just under the manifold on the flat portion of the block. If water is present in the crack, drain the block and heat the area dry. Clean the area well, wire brush and clean again with acetone or lacquer thinner. Mix your JB well and apply rather heavy covering the damage, then let dry. Buff lightly with sandpaper or brass brush, clean again with acetone or lacquer thinner, then apply a second layer of JB, this time extending an inch or so beyond last application. Let it dry 24 hours.

    Check the repair often, but if you take your time and mix well, you should be able to make it through the summer without the much trouble. You already know the problem, and you know it could get worse; however, if it were me and I was not able to afford an engine change right now, I would certainly take my chances on JB Weld rather than sitting out the summer!!! By the way, my repair worked well for well over a year full of fishing and water skiing before I got around to changing out the block.
    "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." - H.L. Mencken

  9. #9
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    Default Re: Marine Tex Or Jb Weld

    Quote Originally Posted by Peaceful Pirate View Post
    Sometimes we can get caught between not being able to do the “right and best” thing and wanting to do something!

    Go with JB. The crack is most likely just under the manifold on the flat portion of the block. If water is present in the crack, drain the block and heat the area dry. Clean the area well, wire brush and clean again with acetone or lacquer thinner. Mix your JB well and apply rather heavy covering the damage, then let dry. Buff lightly with sandpaper or brass brush, clean again with acetone or lacquer thinner, then apply a second layer of JB, this time extending an inch or so beyond last application. Let it dry 24 hours.

    Check the repair often, but if you take your time and mix well, you should be able to make it through the summer without the much trouble. You already know the problem, and you know it could get worse; however, if it were me and I was not able to afford an engine change right now, I would certainly take my chances on JB Weld rather than sitting out the summer!!! By the way, my repair worked well for well over a year full of fishing and water skiing before I got around to changing out the block.
    Awesome. Thank You. Did you ever hear of heating the JB up to allow it to flow into the crack deeper????? I am going to take about 1-1.5mm of surface area off the crack, drill a little hole on either end of the crack to stop it (hopefully), clean with a wire brush, then apply at least 2 applications as you stated.

  10. #10
    Seaman Peaceful Pirate's Avatar
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    Default Re: Marine Tex Or Jb Weld

    There is a great deal of debate on the wisdom of drilling out a crack on a 120/140 block. Personally, I do not subscribe to the traditional thought that these cracks a freeze related as that are far too numerous. I tend to follow the belief that especially in the early 120/140 production, there was some type of fault and/or weakness in area just under that manifold on these blocks.

    As for heating, if the area in question is just under the manifold, I think you will find it difficult to maintain the placement of the JB Weld on the vertical portion of a warm block – assuming you are making this repair with the engine mounted.

    That said, I still find them to be one of the most dependable, reliable and easy to maintain marine power plants available, and with the tremendous number produced, they are very cost effective. The reality is, if you spend some time looking around (craigslist for example), you can find a replacement for your current engine for well under the cost of a remanufactured engine. With a solid $300-$400 engine, and a $350 rebuild kit, you can have a very serviceable power plant for well under $1,000 that will last you many summers!! Hope this helps.
    "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." - H.L. Mencken

  11. #11
    Seaman Apprentice
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    Default Re: Marine Tex Or Jb Weld

    Awesome. Thank You. Did you ever hear of heating the JB up to allow it to flow into the crack deeper????? I am going to take about 1-1.5mm of surface area off the crack, drill a little hole on either end of the crack to stop it (hopefully), clean with a wire brush, then apply at least 2 applications as you stated.
    You are spot on with the repair method. Use a die grinder to clean up the crack a little bit, grind around the crack to roughen the surface up, for better bonding, clean with wire brush then acetone, removes oil.

    I've never heard of heating JB up? I dont know that it is possible once it is bonded. Maybe heat the crack up where it will expand and then apply the JB, when the crack contracts it will "hold" the epoxy better.

    Good Luck! Sorry it was a crack, atleast it was not internal!

  12. #12
    Chief Petty Officer
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    Default Re: Marine Tex Or Jb Weld

    If you are worried about the jb weld running i would use the quick set jb weld.. to me it works alot better on vertical surfaces.

    Just remember as stated in the above posts preperation to the repair area is the key to the repair so dont slack on that.

    I understand the posts saying to replace the block now, "but" sometimes you gotta do gotta do.
    Denny
    1988 stingray svc 207 ss w/ Cuddie cabin
    w/1987 mercruiser 5.7 thunderbolt IV ign. alpha 1

  13. #13
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    Default Thank You

    Folks, wanted to say thanks to all that replied to my issue in regards to my 3.0 being cracked. Hopefully, the temp fix will last the summer. Will let you know by weeks end. Semper Fi

  14. #14
    Lieutenant Junior Grade danond's Avatar
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    Default Re: Marine Tex Or Jb Weld

    FYI It's not a $4K repair. More like $1500 to R&R the block.
    1989 Starcraft 171S Select "Cap'n Crunch" / OMC Cobra 4.3 V6 / 432APRMED

    If you're going to keep that OMC Cobra, please for the love of everything good in the world, get an OMC factory service manual. Not a Clymers, Not a SELOC. You can find them on eBay.

    My boat repair website: http://transomfix.dcpolk.com


  15. #15
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    Default Re: Marine Tex Or Jb Weld

    I am just going to have a long block put in (someone will do this for me, probably the dealer). I know car engines and the like, but the marine application engines and how to disassemble what is required is null in my know how. Plus the space you have on a boat sucks.

  16. #16
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Marine Tex Or Jb Weld

    What do you have there, other than a 3.0L Mercruiser, OMC, Volvo? What year. There are service manuals available that make the job understandable.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  17. #17
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    Default Re: Marine Tex Or Jb Weld

    Quote Originally Posted by Don S View Post
    What do you have there, other than a 3.0L Mercruiser, OMC, Volvo? What year. There are service manuals available that make the job understandable.
    2005 3.0. I don't have the facilitiles to pull the engine. On a lift out on a pier. Easier to take it to a dealer.

  18. #18
    Lieutenant Commander fat fanny's Avatar
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    Lightbulb Re: Marine Tex Or Jb Weld

    Three years and still running knock wood. 3.0LX crack below the manifold had it welded by my cousin (engine builder) The key to welding any cast is the using the right filler material and proerly pre and post heating the surface area (SLOWLY and not to hot) He layed down a perfect row of nickles in a nicely concave rut where the crack used to be and ground off the excess it's all in the process something to think about @ least untill you can afford to replace the block if thats the route you take. Good luck
    1996 Searay 175 Five Series
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