The one comment I would make is that if you have any coring beneath the fiberglass, such as plywood below the fiberglass deck, you must make sure the holes are absolutely sealed tight. Otherwise you'll suffer major lamination of the deck after water rots the wood.
Water is a tough thing to keep out of a boat sometimes.
MarineTex is a favorite repair, and it is simply an epoxy, so it will seal the holes good enough if it is properly applied. The only problem with using it for high-stress screw repair is there is not much bite in epoxy, and the screws might strip out again.
A good alternative in this situation is to embed some loose strands of fiberglass in the hole, then use a non-paste epoxy, such as West System to fill the holes. The fiberglass in this regard will provide some bite to the screw threads.
But with either repair, the best practice is to "bed" the hardware with a high-performance adhesive, such as 3M101, 4200, or Boatlife Caulk to ensure water does not get into the decking.
So its a two step process - 1. seal the hole with epoxy, and 2 - bed the fitting with a sealant. If you do this, you won't have a lot of screws backing out.
I would not use Silicone, such as RTV (the stuff that smells a bit like vinegar), to bed the screws, it doesn't have good enough sealing properties. Silicone requires constant compression to maintain a seal, while 4200/5200 is a high performance polyurethane, and 101 is a polysulfide, both of which make a "hard seal", are normally preferred for bedding applications.
One caution on 3M 5200, if you use it, the screw might be permanent. While this is normally the intended purpose, if you ever need to remove the thing you screwed in - it might be next to impossible. For that reason, 3M makes 4200, which has the same sealant properties, but half the adhesive strength of 5200.
But I had a Windlass I caulked on the deck with 4200, and had a very hard time taking it off, even with 4200. There is an aftermarket product, called JW Antibond 2015 that you can get at West Marine. It pulverizes 4200/5200 and most other sealants, and it will allow you to remove the screw if you need to later.
