Poxy Epoxy ....problem you got an answer?

[pistnbroke]

I was re building an outboard water pump housing .fitting a new liner into the bored out housing . Very tight fit but glued in with epoxy ..two tube stuff 5 min ....baked in oven at 50 deg C for 20 min .....now its got wet the surplus in the housing has gone all white and soft...
Is it

poxy epoxy
not enough /too much harderner
or what ?

[PAR]

Epoxy is unlike polyester, in that you can't vary the hardener content to suit different situations. Either you have the correct ratio or you're screwed. This said epoxy does offer some latitude in that you can be off the ratio by a little (a few percent) and it'll still cure. If off the ratio by more then this, well, as I said . . .

If the epoxy is soft, it's not cured, especially after post curing. So, if you added or subtracted a little hardener for what ever reason, thinking you'd be doing good, your screwed and the epoxy has to come out, the surfaces cleaned and the next patch, a perfect mixture ratio. You can't fix this. No amount of addition hardener will solve this, it has to come out.

If the epoxy was hard when the sleeve was installed, but then changed color, well this is probably heat/water contamination. Epoxy will start to deform at about 65 c and becomes considerably less able to stick and hold onto stuff. I can see the inside of a pump housing reaching this temperature, though it is a bit of a stretch.

The question you have to ask yourself is, did you screw the mix ratio or not.

[pistnbroke]

Very carefull to mix equal lenths of tube squeezing ..dont see how it can get hot as its cold water in and a rubber impeller ....

are you saying its just a bad mix ..if so I assume you mean too little hardener ..gone white like a boiled egg white... the bit that did not get wet is hard and green ish

[PAR]

How hard (which is what my other half constantly asks, but I digress)? Can you dent it with a fingernail, pushing as hard as you can?

I've used tubed epoxy and made precise lengths of goo, just to find it wasn't right and didn't cure. You have to measure volume or weigh it. The eyeball method doesn't work, especially with small quantities. For example lets say you need just 30 milliliters (about an ounce) and it's a 50/50 mix. You put 16 milliliters of resin and 14 of hardener in the cup. Being off by just 1 lousy milliliter on each part, which is pretty hard to gauge by eye (about a 7% error), this is enough to screw the pooch.

If the goo that wasn't contaminated is rock hard, then I'd just cut off the milky stuff and call yourself lucky. If the non-discolored goo isn't hard as my ex-wife's bunions, then you may want to see how long it lasts before you have to dig it out of there.

[pistnbroke]

here is the location ..I dont think I am going to scrape it out ..it oozed from the joint at the junction of vertical and horizontal surfaces ...you can see its a 3mm ali liner turned down in situ to about 1 -1.5mm to re con the pump......

I have a new version on hand .A sheet of 15 mm PTFE sandwitched between two stainless sheets for I hope a long life pump body ..Chrysler did not make a stainless pump housing

[Herman]

Buy yourself another type of epoxy. The 5 minute stuff is only designed to cure in 5 minutes, not to be really water resistant, strong or anything.

modellers like it much, but most models do not see much water or forces. It also is great for all kind of low-tech repairs. For your water pump I would suggest another epoxy though. Basicly any marine laminating epoxy will be OK. It will not cure that fast, but a couple of hours at 50C will speed up things. Or leave it to cure for a couple of days.

@PAR: not all epoxy will turn soft at 65C. Many epoxy types go over 80-90C, and even higher. At this moment I have a type available which has a Tg of over 240C.

[pistnbroke]

Thanks for that ..dont buy at the pound shop then !!!! Have a new design thats epoxy free using a PTFE slab with two stainless plates one above and one below ...photos if you are interested or anyone wants to comment