Thanks all. What is the best filler? Here are the options from West
System's User Manual, in descending order of hardness/strength:

403 Microfibers (strongest adhesive filler).
404 High-density filler (the manual recommends this for hardware
applications).
405 Filleting bond.
406 Colloidal silica (this is their less preferred filler for hardware
applications).
407 Low-density filler (microballoon, not recommended for this
application).
410 Microlight (not recommended for this application).

The optimum would be a filler that I could squeeze into the hole using
a syringe after mixing, but when it cures will be hard enough to hold
the screws and prevent water penetration.

My transducer model is a breakaway type, by the way. It is designed
to fail before the screws if the transducer hangs up on an obstruction
in the water.

Jim

On Sat, 24 Apr 2004 00:53:03 GMT, "Lew Hodgett"
wrote:

3) Mix some epoxy with micro-balloons to a rather stiff mix and stuff some
in each hole. Don't try to fill the entire hole, you'll be wasting your
time.