Epoxy Emergency 911 call if you can

If you are an epoxy (West Systems) expert and can spare a minute and a phone call pls call. 7:20 PM CDT. I'm at the boat and the stuff is smoking. Too hot to touch the deck that it is under. Got the fire extin. out just in case.

OK, now that the smoke has subsided here's what happened.

I had removed the waste pump out deck fill (2" deck cout out) with the intent to replace and rebed. I decided to fille the whole thing with epoxy and then use a hole saw to reopen the deck fill opening. I removed the balsa core out from around the opening (about 1/4 to 3/8 inch all the way around). Wiped the underside with mineral spirits (let dry). Used Gorilla tape on the underside to seal the bottom of the hole. Used mineral spirits on the top deck and swabbed the inside of the hole with Q tips. Used 3M blue tape to tape around the hole as well as covering the 2/3 of the hole nearest the toe rail (to keep the epoxy from running "down hill" as it filled the upper side of the hole. Mixed the West System (105/205/406). Filled the outer rim of the hole using the syringe. Had to mix another batch of epoxy (took less then 3 or 4 mins). Poured this epoxy into the hole. It started to smoke a little, then it started to smoke a lot. The tape covering the hole appears to have turned brown a little and over the hole itself it was hot enough to burn skin. Even through the surrounding deck material you could feel significant heat build up. By the time I went below to get a fire extinguisher (15 to 30 seconds) the epoxy had expanded slightly and had set enough that I couldn't scrape off the bulge that had now formed. After a couple of minutes the smoke subsided and after a couple of more minutes it appeared to have started to cool off. WOW.

I'm fairly new to epoxy fills and have only done stancion mount holes up to now.


Does curing epoxy create this much heat normally?

Did I pour to fast?

Interaction with some other substance?

I have another deck fill to go and would prefer a little knowledge before proceeding. Thanks for anyone who replies (and the phone call is no longer neccessary).

sv.Island Girl
Even now about 30 mins later, cupping your hands above the hole, it's like putting your hands above a warm cup of coffee. Perhaps too much epoxy and not enough room to vent the heat? I don't know.


Member III
Sounds somewhat normal

I do not have experience with that specific epoxy, but I do have epoxy experience. It will develop a lot of heat. The greater the volume you mix, the greater the heat will be. I'm a little surprised about the heat that you created, but I've seen maple bench tops burned from cups of epoxy sitting on them.

In the future, you might try several thin layers with cure time in between. This will keep the heat down.

How's your heart rate?

Hope this helps.

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Sustaining Partner
Welcome to the wild world of exothermic chemical reactions. The larger the batch of epoxy, the faster the heat buildup will occur and the faster the whole thing will "kick" or harden. I only use 205 for dead of winter, thin coats or small, like a few ounces, batches. Everything else gets 206 or 209 hardeners. This will keep the heat under control.

When I fill something like the project you just did, I do it a little different. First there is no reason to fill the entire hole just to drill it out again. Epoxy is not cheap so why waste it? Mix up a batch of resin. Brush the resin into the cavity you intend to fill. Just coat the inside of the cavity. Now mix filler into the remaining resin until it has the consistency of peanut butter or cake frosting. Do not eat :p Now use putty knife, tongue depressors, etc. to "pack" the thickened resin into the cavity. I usually leave the thickened resin "proud" or protruding slightly from the cavity so I can clean it up with a hole saw, grinder, drill bit, etc. when it has hardened. Does that make sense? Hope it helped. RT


Innocent Bystander
I've had epoxy cook off like that a few times but it's always been in the pot, not on the item I'm working on. It's pretty scary, and the characteristic smell before it really starts getting hot gets my heart pumping because that smell means either you have to finish whatever you're working on RIGHT AWAY, like within seconds, or you're going to have to mix up another batch of epoxy.

I pretty much always use the slow hardener now and this becomes a lot less frequent.

Tip: if you can get some "Mighty Putty" or the equivalent, it isn't too hard to flatten a pancake of it to use as a plug in the bottom of your holes. It cures very quickly and seals better against wet epoxy. I haven't used Gorilla Tape specifically for this application, but wet epoxy sometimes dissolves the adhesive on other tapes I've used well before it cures.

Once you get the hang of it, epoxy is really great to work with.
Thanks for the replies, phone call, and information. I guess I missed the part about the heat buildup in the instructions. Well one more hole to go, but with this new info it should go better.


Member III
SOP for epoxy in a volume -- I've melted many a cup with leftover epoxy. Good advice here -- here's another tip that will keep the heat down when filling a hole, especially ar bigger one as needed when closing up a thruhull for example. Fiberglass tends to not like temps above 200 degrees, so... Take a plastic cup, pour mixed epoxy into the bottom, let it kick and harden, then pop it out. It should come right out, but you could give it a squirt of release wax if you want. Then clean the disk -- for either the amine blush or the wax -- and rough it up a bit with some sand paper for tooth. Put a layer of mixed epoxy in the hole, put the disk in, and add the rest of the epoxy. That way you reduce the amount of unkicked epoxy in the hole, and also the volume is spread out so the heat will be turned down.


Contributing Partner
What I want to know is, during all this drama, how did you have time to log into the forum and make the post?


Reminds me of the TV commercial for the home alarm company where the girl is alone, the bad guy tries to break in, and as she is running through the house (ostensibly to escape?) she stops to answer the phone when it rings.

"This is the alarm company, is everything OK?"

It was until I stopped to answer the phone and the bad guy caught up with me...


Sustaining Partner
One of the great benefits of my method is quite often the bottom of the hole need not even be covered with tape. If the filled epoxy is thickened to "peanut butter" levels it stays pretty much where you put it. I've yet to find anything that will completely seal against straight resin. That stuff seems to leak everywhere.

Regarding the "peanut butter" approach - I was thinking of something similiar (as I was puzzeling over how to fill a down hill void clear full of epoxy without it running all over the deck) but I wasn't sure enough of the epoxy that it would seal the balsa core against water intursion of it was that thick. I'm asusming from your response that it would.

Regarding the resin leaking everywhere - I tend to concur. On the 4 bolt holes for a stanchion mount (not the one with the emergency) I kept filling and filling (a total of 3 105/205 pre mixed packages). The epoxy wasn't running into the cabin but it was apparantly "seeping" into the balsa. I guess this is a good thing.

Regarding the use of Gorilla brand duct tape. I've used it for 2 deck fills (1.5 inchs in diameter) and 2 stanchion mounts (4 bolts each) and have had no below deck seapage. Even with my "cook off" emergency the heat didn't weaken the Gorilla tape bond below decks.

Regarding the question about how I had time to post during all the drama - Well it's like this. Once I had the fire extinguisher out, and the smoke was still coming off the mix, I had nothing to do until flames burst out except stand around or try to find out how badly screwed I was. I elected to find out how bad off I was going to be - and what better place to do that then with you fine, knowledgeable folk.

And in closing - This evening I completed the Epoxy fill of the other deck fill. Thanks to the information learned from here I managed to not stress out, not burn down the boat, and not even break out the fire fighting equipment. I did fill the entire hole with epoxy (even though the peanut butter method would have been more cost effective) but did it in smaller increments so at to not generate as much heat. It seems to have set nicely and tomorrow I'll drill them both out and install the deck fills. Someday soon I hope to have a boat with no topside leaks (dare to dream) and nicely sealed deck holes.

Hopefully, if nothing else, everyone has had a nice laugh from my breif drama. Maybe someday I'll actually be able to give advise on this forum rather than sucking it dry form everyone. Thanks all.


Innocent Bystander
While you're thinking about resealing those holes, look up Mainesail's post here on the miracles of butyl tape vs. polysulfide sealant. I'm a believer: inexpensive, easy, very effective, not messy.


Member III
Yes, butyl tape

I was just going to suggest that you consider using butyl to seal the fittings. It is very reasonable and I've heard great things about it's ability to seal and stay plyable.

Good Luck,

I read the article on rebedding on this site and have followed it, the dremel bit, the counter sunk holes, and the butyl tape. The article was great, the procedure gets easier the more holes you fill, and hopefully the result will be no more water penetration.


Junior Viking
I've had exactly the same reaction with MAS epoxy as well.

All was going well with the pot when the reaction started to go way to fast and smoke came out. I was also working in the general "head" area.

My belief is that you did the same thing I did, your brush, tool etc. picked-up some other chemical that speed up the curing. Bleach, Tidy bowl, etc. who knows...

But it was enough to scare me too. Had small enough pot, but it melted trough the plastic container.

Best to make sure all surfaces are clear of contaminants.