I am a firm believer of using the products recommended by the paint mfg. Ie: interlux stay int the line. Interlux faring compound is for above waterline. In the interest of saving time.. go to their web site they have detaile applications.

dave

DOUG,

I am a epoxy rookie. I need to waterproof and seal a 3" laminated outboard mounting board on my sail boat. I also want to try the micro ballon filler on my Marinette. I would also like to try out Jeff's sanding method to seal up bare aluminum. There is no marine store near me. I found can (about a pint) of 3M Bondo brand epoxy at Wal-mart. It was only $12. The can said to use Acetone, which I have, for a thinner. My questions. What is the shelf life of epoxy, can I store a larger quantity? Do I have to paint over it to protect from sun? Wouldn't 3M make a good enough quality product for my purposes?

I don't know if Bondo brand epoxy is much good under water, but is likely OK for use above the water line. Bondo products are not designed to be immersed, they are intended for car bodies. Check the label - if it doesn't say that it's good under water don't use it there.

You can get WEST epoxy from any boat store, I like Hamilton Marine in Maine but West Marine is OK. Get the cans and the pumps to go in them, and a bunch of little plastic cups and exam gloves. The WEST system includes various fillers - so it is versatile and there is no question about it being marine-grade. On the other hand, the stuff is expensive.

It is handy to get stuff with the filler already in it. I haven't used PC-7 but I would consider using it after Jeff's recommendation.

As for the outboard mounting board, I would:

rout the edges to a nice radius
drill holes oversize and fill with epoxy/filler
saturate with liquid epoxy using a disposable brush
then sand smooth
Lay 6 oz. glass cloth on top and saturate, working around the edges as much as possible. It helps to trim, slit, or pull out fibers to get around the radius as far as possible.
when hard, turn it over and do the other side.
sand the fuzzies off.
using fiberglas tape or cut strips, cover the edges and overlap the glass as much as possible.
Redrill the holes to the size needed. This leaves the hole lined with epoxy, not endgrain.
paint to suit.

I have done this a lot. Frankly, I don't have the patience for it anymore, and I would buy a piece of StarBoard and make a plastic one. The plastic is heavy but lasts forever.

That 3M epoxy I found at Wal-Mart was a liquid resin with a tube of hardener. Instructions on the can covered how to glue down fiberglass cloth. It was not the Bondo putty. There was also a boxed kit with the same resin that contained instructions and a piece of fiberglass cloth to patch a hole in boat. For $12 I am going to try it out. I like smaller quanities I can use up quickly. Some of these chemicals have a short shelf life expecially if you leave them out in the cold. I had to throw away an 3 year old can of varnish. It would not harden anymore. I now keep all my paints, glues, spraycans and finishes in the house.