Can this be JB Welded/ Epoxied? Seeking Opinions

**ProXR6** · 11-03-2021, 01:22 PM

1999 Mercury XR6 Carb'd
S/N: 0G825341

Had the #5 piston come apart at WOT and pieces of the piston skirt slammed into the crankcase cover resulting in a quarter sized hole. I'v attached pictures of said hole and piston. Crankshaft suffered no damage thankfully so i am going to rebuild. My biggest obstacle however is this hole in the crankcase cover. Aside from crankcase compression, this area of the crankcase cover does not seem to be a high stress area.

Does a JB Weld or Epoxy type repair seem practical in this situation? Would welding it be better? Any/all opinions are welcome.

- Thanks

**Stoker boy** · 11-03-2021, 02:54 PM

I’ve TIG welding those before I don’t know how JB weld would last. I’ve seen it done with a wire feed because TIG welding does build heat. You definitely want to heat that area up prior to welding to get any permeated oil out of the metal. If I remember correctly I used a thick piece of copper on the opposite side build everything up and then mill it down, never had a problem.

**LakeFever** · 11-03-2021, 03:10 PM

Seeing as epoxy holds up well covering the oil injection cavity I think you could epoxy that back together ok. Id be sure the backside has loads of contact and fairly thick to give it more strength. As always the bond will only be as good as the prep

**sonicss33** · 11-03-2021, 07:31 PM

That is an easy repair if you find an experienced TIG welder. Build it up, fill hole then grind it smooth.

**LakeFever** · 11-03-2021, 07:59 PM

I agree it would be easy to weld but all that heat might not be so easy to keep everything true which leads to bigger problems. I’d epoxy or replace if it were mine.

**Bodhi** · 11-03-2021, 10:10 PM

Originally Posted by Stoker boy

I’ve TIG welding those before I don’t know how JB weld would last. I’ve seen it done with a wire feed because TIG welding does build heat. You definitely want to heat that area up prior to welding to get any permeated oil out of the metal. If I remember correctly I used a thick piece of copper on the opposite side build everything up and then mill it down, never had a problem.

Copper plate as stated above, and you can get welding clay from any weld supply store. The clay will absorb the heat that radiates from the weld area

**Jay Smith** · 11-04-2021, 06:13 AM

I’ve had 100% success on the cold side of the 2.5 blocks using A-788 2 part epoxy for over 25 year with zero failures as stated on # 2 oiler cavity….will work on your cold side issues !

Jay @ JSRE

**cali kid** · 11-04-2021, 07:31 AM

I use West Systems epoxy with fabric. Grind around slightly, use tape as a backer. Then over lap the fabric a little on the first side of the hole. Apply the epoxy with a small brush. When it sets, flip it over and repeat. Done many, never had a failure.

**Chaz** · 11-04-2021, 08:17 AM

I've got tubs of Splash Zone , PS-7 , PC-11 , Marine-Tex , tubes of Devcon , JB Weld , Moroso A-B epoxy .. and probably a few more. What none of them will do is show where the cracks radiating from points of impact have spider webbed to .. like heat will. From the looks of this picture , it appears to go from boss to boss and down to the little bomb crater.

Unless you don't mind having fractured parent material under a slab of glue , the best repair is to tap out the broken material .. shape the hole with a carbide burr , make a piece that fits the hole . Weld it in place sand the inside , paint the outside .. done.
Any competent welding shop can do this .

As far as playing Mr. Dairy Queen .. first , there is no where to put an inner backstop , second it's thin material so it will be rows that most have to make thicker as they stack them .. so it will go from about .090 to well .. I've seen it all .
Corn rows also tend to put a lot on heat in a small area , expect the site to shrink as it cools , if you don't tent it , and let it come back slow .. it could crack as well.

I made a big-azz plate that I can bolt 2.5 and 3.0L blocks , front half's and adapter plates to. So no distortion ...

That hole is nothing , I'd be more concerned with getting rid of the crank ring trench's ...

**FUJIMO** · 11-04-2021, 08:40 AM

...I'd be more concerned with getting rid of the crank ring trench's...

...how chaz?...

**ProXR6** · 11-04-2021, 09:02 AM

Thanks for all the suggestions. I do have another used front half on the way that i will attempt to fit with the dowel pins removed. I've got most of my eggs in that basket, but if for some reason i can't make that work, fixing and reusing the original may be my best option, and i feel a lot better about how that hole should be fixed now.

I am also interested in the best way to correct those sealing ring trenches mentioned above....? I'm sure you guys have some clever tricks for that..

**Dave S** · 11-04-2021, 09:14 AM

That hole goes to a blind area,,,,, fill it up and go on........Don't change the front have,,,, the sealing wear woun't match.....build it cheep ......quick runn the shipm out of it.......

**Noah Burns** · 11-04-2021, 10:10 AM

when you guys say "cold side" do you mean the front half in general?

**Chaz** · 11-04-2021, 12:12 PM

Originally Posted by FUJIMO

...how chaz?...

Part of my graduate study from G.O.B.I.T. (good ole boy institute of technology) taught me that I can't walk into NAPA and buy the specialty tools I needed.

So I built my own ...

Recessed ring brings the old strip of glued belt up to flush diameter.
The width of the drum spans the rib being sized and at least one more at the least, but for most , two ribs as guides.

I have went into motors that had tell-tale signs that they have been gone thru before. Some of them had broken sealing rings. Maybe you can detonate a motor so bad that it will shift the case half and snap the rings .. but I think a 2 stroke would break/ stick the piston first.
So I'm going with maybe a different crank was used ... or the sealing rings were taken off everything cleaned up and put back together with the rings in different locations. Maybe some made it in the blocks "groove" but not the front half's "groove" . Side load them enough and ""bink"" broken rings.
I just know , that if I remove the groove .. lap the crank rings , they all get bedded in at a fresh location of it's likening (less rotating friction).