Another epoxy-filler lower unit-question...

[Hydro-T20]

Hi again!

I`m currently i the process of filling up the bob`s nosecone/lower unit-joint with epoxy filler...
This time I have taken my time and really cleaned out both the cone and unit with sand paper and a steel-brush on the electric-drill-thingy, washed out with Acetone and applyed the rimer for the epoxy.
The filler is called Lefant Marine Epoxi Filler and it is West systems that stock it for some reason, should be a good filler I thought.
The thing is that it requires(?) primer for a good bond with alloys, but the lefant primer was not in stock when I was in the shop, so the guy gave me another primer -also for alloys.
Now to the question, have any of you guy`s ever used this type of primer when using epoxy on alloys? the stuff comes in two cans, base and adhesive...but it looks all shiny and stuff when applied.
This was not what I expected..shouldn`t it be more bond with a rough surface?? Or is it some kind of chemical bonding-thing?
I`m gonna leave it on until tomorrow and see..

The stuff seemed quite powerful, and had lots of warnings on the back of it....do not get on skin, eyes etc..(almost all chemicals do, but somehow I got a feeling that this stuff was a little more powerful than usual, not to mention the smell of it Mask and all windows and doors up in the workshop..

Yes I know it should have been welded, and I should have bought a sportsmaster..but the money aint there for the master and welding is not my good side...

[brotherxb03]

I have a bob's on my allison that needs redoing again. I think this will be the 3rd or 4th time. I'm tired of redoing it. I took it down to the metal twice. Tried the bob's expoxy, JB industrial weld the 2rd time. After about a year it blisters again. It held up a little better last time cause I shot it with urithane paint.I would like to get a sportmaster also,but can get tatooed easy buying used.

[Liqui-Fly]

If your using epoxy and you take the gearcase down to bare metal, you have to etch the aluminum. Essentially its high powered cleaning of the oxidation on the surface. This oxidation isn't a good hard coat like chromium's oxidation product. Essentially if you have an etch kit from someone like West System, you have an acid to clean the surface and a part B base to neutralize the acid. You do not get a chemical bond so yes a fairly rough surface aids in bonding, but remember it is surface area dependant so 36 grit isn't necessarlily better than 80 grit paper. From what I've read and what I've done, 80 grit is adequate, maybe the best. Most importantly, 99% of off the shelh 2 part epoxies are amine cured which means you can get an amine blush on the surface during cure. This bluch isn't soluble in most hydrocarbon solvents but is very soluble in water. After the epoxy has cured for a few days give it a nice soap and water bath and allow it to dry. Wait a few days...maybe even a week and see if the blush comes back. If it does repeat the above. Epoxy does not work like most polyester based body fillers and takes time to fully cure. While it will last much longer if care and time aren't given before paint, you'll never get a decent, lasting finish.

[hsbob]

i have not had any problems with using the epoxy on clean roughed up alumium on LU. the biggest problem is the cracking of the epoxy between the LU and the LW addition. i do not believe any ready made filled epoxies are going to work, since the thermal expansions are too different. im going to fill epoxy with milled fiber in an attempt to cover the problem.

[Liqui-Fly]

i have not had any problems with using the epoxy on clean roughed up alumium on LU. the biggest problem is the cracking of the epoxy between the LU and the LW addition. i do not believe any ready made filled epoxies are going to work, since the thermal expansions are too different. im going to fill epoxy with milled fiber in an attempt to cover the problem.

Glass milled fibers or colloidal silica make a significant impact on the epoxies CTE. Using an unfilled or lightly filled resin in this application is a bad idea.