The Stovebolt Site Forums The Shop Area Engine Shop Marine Tex

This product has been recommended here as being a superior patch over JB Weld for cast iron block cracks.

What is the exact kind needed? White? Gray? RM302K ? RM303K? etc. etc.

How much is enough for typical repair down by petcock on 216? This crack barely seeps and was repaired a long time ago by someone else. Ham Handed job with huge pile globbed on. I see 2oz for $25, 14oz for $51, bla bla

They recommend gray for machine repairs. I’m guessing the smallest size would be enough. I’d grind a vee in the crack and drill the end. Clean it with acetone. Jerry says use a piece of sandpaper pressed over it to mimic the texture of the cast iron.

I used the grey as recommended here a couple years ago and used the sandpaper trick. Drilled both ends and ground out the crack. Worked perfectly. Get a bigger container of the stuff- it’s good for all kinds of other things

yes = on getting the "bigger container" = this stuff IS very useful. I have been using "Marine Tex , since the mid 70's ............... I have 'patched several gas tanks, with this .....................
and , just afew months back , patched my 69 Nova fuel tank - - from a can that I have had for over ten years (yes , keep them sealed up , and they last for years.
It's a "two part mix" = a can of 'putty & (either) a can of hardner (or in a glass jar) . Maybe they don't use the "glass jar, anymore . . . but . . . my point IS ; if you buy a bigger container ; just make sure it stays sealed up (while you store the left-over) .

On my 53 I H p/u , I sealed a leak (on the side of that tank) way back in the 'mid 70's . . it is still good to-go !
We use to use those "fiber glass tank repair kits' , at work , for fuel tank repairs . . . they would not hold up .
Back in my 'body shop days' , we found this Marine Tex , too 'patch the old Buick & Pontiac front Headlight (fiberglass) 'header panels' . I'm a real believer - - now , it's costly - - but, a very good product (for
everything) .
On one of my old qt cans . . . it even says "For Engine Block Repairs" . I have always used the "grey products" .

jim

Otto . . I would not put this "over an old repair" . . . . clean that old stuff off , and then apply your Marine Tex .
(if the old product is not doing the job - - clean that stuff off ! ) .
Make sure too clean your damaged area very good (and if it's roughed up , the better) .
jim

Diffinately don't apply the Marine Tex over any old repair, I have repaired exhaust manifolds, cylinder heads, blocks and tractor engine parts for decades using this stuff. Whatever repair needs to be worked, sand with real corse paper, and yes stop drill the ends and V edge works also. Pneumatic air and even a corse file has worked for me without any problems. Make sure the repair is real clean before you apply the M.T..

Otto, is this the same engine that you have had mysterious cooling issues?

Yes.

The old stuff was working until the overheating issue seemed to soften it up.

I am grinding/sanding it off to bare metal with a Dremel tool.

How should I clean the area when finished prior to application of the Marine Tex. I intend to use degreaser and soap and water to clean up the area and then dry it thoroughly. Anything else I should do or not do?

Otto, I've seen recommendations to heat the block with a propane torch to drive moisture and oil out of the cast iron prior to painting. Doing the same for a Marine-Tex repair sure wouldn't hurt in my opinion.

That sounds like a good idea.

Otto - Are you draining down your coolant so no seepage during Marine-Tex repairs??? When you remove the old patch material, it will more likely than not allow for seepage/leakage which will prevent the patch from adhering properly.

Yes. I'm leaving the water in it while I sand and grind off the old stuff so I can see the water seeping from the crack. Once I'm done, I'll drain it and clean the area.

Before you apply the Marine-Tex, hit the area with a torch (about 150°) to sweat out any oil/moisture, then clean it with a preps-all.

You could use a propane torch.

EDIT: Kevin beat me to it!

Will do.

I have used eighter lacor thinner or acetone with no failures.

Good to learn of a new (to me) product. Anyone know how Marine Tex compares to Devcon epoxy?

I do have a partial can of Devcon and activator purchased a few years ago that's still good. I used it to take slack out of a backhoes front spindles. Hadn't considered using it on the '64 CJ5s gas tank but may if the leak pops back out if/when the fiberglass plus JB weld patch fails.

RonR

I just discovered that Devcon and Marine Tex are made by the same company, ITW Performance Polymers. The Devcon line includes a bunch of different products as well as epoxy putty. They advertise it for machine repairs like you did on the backhoe. That would generally be with a steel-filled epoxy.
They recommend Marine-Tex for fiberglass repairs (I've used it on my fiberglass boat and can report that it works well.) Here's the blurb from their website: "Marine-Tex is the legendary high-strength repair compound designed for filling, bonding and rebuilding wood, fiberglass, ceramic, glass, metal, masonry and many plastics."
My guess would be that a Devcon steel-filled epoxy would be just as good for a block repair as Marine-Tex. [on edit]This might be a concern on a block crack repair. From the Devcon Plastic Steel TDS: Temperature Resistance Wet: 120°F (49°C); Dry: 250°F (121°C). ITW doesn't report temperature resistance for Marine Tex.

The label on Marine Tex shows a block repair like I plan on doing and the instructions list water jacket and crankcase repairs as something to use it for.

Otto, Not saying you can't use Marine Tex for your block repair. I was just digging out info in response to RonR's question about Devcon. Isn't more info a good thing?
Good luck with your block repair.

I remember using Devcon Epoxy Aluminum and Epoxy Steel at least 40 years ago, somewhat before Marine Tex came along. Both of them are very good quality products. A similar product used in the gunsmithing business for bedding rifle actions is called "Acraglas". It's a 2 part epoxy which can be mixed with atomized stainless steel powder to make a rustproof metallic filler. It's quite a bit more expensive than the other products, however.
Jerry

How thick would you guys make the repair? I don't want it it all globbed on like the previous repair but I want it to last. Box says you can go up to an inch thick. I was thinking 1/8 to 1/4" thick and going 1/2" - 3/4" past each side of the crack.

Interestingly the instructions say thicker applications dry faster than thin applications.

I don't think thicker than 1/8", or even that thick would be necessary. You just need it adhered well to the surrounding area, and if you vee out the crack, that will help with adhesion and sealing. Like has been mentioned above, prep and cleaning is very important.
Thicker applications do cure faster, but that isn't really an issue or an advantage, as it's a chemical cure. You do need to keep the block warm, may be put a radiant heater on it before and during curing. If it's too cold it won't cure well.

Most epoxy compounds are "exothermic"- - - - -they generate heat chemically as they cure. Thicker layers retain more of the heat of curing instead of radiating it out into the surrounding material. A layer no more than 1/4" thick should be all that's needed for a good bond and enough strength to resist the pressure inside a stovebolt cooling system. Press a piece of 40 grit sandpaper against the patch just before it cures fully to mimic the texture of the surrounding cast iron.
Jerry

I applied the epoxy a little while ago.

I've used JB Weld before and am familiar with its drying time, etc. I've never used Marine Tex. How long before it is hard enough to mold or touch up cosmetically?

Also, it's Marine Tex Grey. I kind of expected it to turn grey when the resin and catalyst were mixed - sort of like Bondo. It didn't change color and stayed black, which makes it harder to tell if it's mixed properly. Does it turn grey when it cures?

Temperature in the garage is about 70-75.

Here's the info from their website: LINK

I have only used Marine Tex white, so can't say about any color change when mixing. Is the hardener a different color than the base material?

Hardener gel is sort of amber color. Resin is black. Anyway, it's pretty much cured and is still what I would call black rather than grey.

Doesn't matter. I guess this will be my excuse to clean up the engine and paint it grey instead of the black that it is now.

The epoxy has cured and there are no leaks. Test drive was successful and 180F was achieved and never exceeded with no problems with the epoxy, leaks, overheating, or anything else.

I'd post pics of the whole thing but my phone no longer wants to co-operate with my computer to download pictures.

I guess I'll drain the water and refill the cooling system with anti-freeze.

yes , I agree with Kevin (above) . . . . just make things "dry & clean" before you make u'r repair. I also think the Marine Tex DOES sitck very good - so, I would think - u'r good to go .

(give us a 'follow up' , on how it works for you & your truck) - Thank you .

jim

note : if you were too pre-heat your block ............... then, you better work quick (the heat will make things much faster "drying" ) = just be-aware of that issue, and plan ahead .

See post above yours.

Truck now filled with anti freeze and 10 mi test drive. Ol' Roy is back in the rotation for daily driver. Gotta install the rebuilt speedometer.