Not where I'm running a fastener back in, holes left from abandoned transducer mountings, etc. I realize that maybe 5200 with the fastener back in is probably a permanent solution but I'm just curious what others do if the fastener is to be left out.  I'm talking 1/8" or so hole, not a hole you'd be left with after removing a thru hull transducer or anything.  What do you guys like for the job? 

5200 will fill a 1/8 hole easy without a screw in it.

Try this.....

 

Marine Tex will solve the problem. Once it sets up you can lightly sand it and actually paint it to match the boat if you want.