Filling Screw Holes Below Waterline

[MPKehoe09]

What does everyone use to fill old screw holes above/below the water line?

When putting a screw/fastener into the hole, i've been using 3M 4200 (New trim tabs, relocating transducer, replacing scuppers).
However, I've also removed old fittings (swim ladder, old speedo, old transducer) and wish to fill these holes.

If I've already got the 4200 opened, can I get away with filling 1/8" and 1/4" holes below the waterline?
Or should I use something like Marine-Tex?
I don't have any prior experience working with fillers/resins, (West System, etc.)

And on a somewhat related topic, once you puncture the seal on a tube of 4200, is it true that it only has a 24hr shelf life?
I hate wasting 95% of the tube when I only need to use it for a handful of fasteners, and practically throw away $15.

Is there a better product similar to 3M 4200 that I can use that can be mixed to the required amount needed?

Thanks.

[wingtime]

Do not fill old holes in the transom with 5200 or 4200. Overtime they will allow water intrusion into the core. For below the waterline small screw hole repairs this is what I do: Drill the hole slightly larger and then countersink it a tiny bit (this gives tooth for the filer and prevents spider cracks). Fill the hole with epoxy thickened with milled fibers or cabosil. I use epoxy because it is impervious to water and it will soak into the exposed core and seal it permenently. Marinetex would be my second shoice.

For larger holes such as a bolt hole you have to fill it with something. Some use dowels but this not the proper method. The reason is the grain is going the wrong way and is not compressible like the original transom core. This can lead to the dowel popping out the repair if the transom is compressed near it. Instead make wooden (or composite) plugs to fit the hole using a wood plug cutter bit. Lather them up with epoxy and put them in the holes. Be sure they are recessed a bit so you can patch the rest of the hole with epoxy and glass.

You can extend the life of your 4200/5200 by putting it in your refrigerator.