I see that there have been quite a few views to your post ... but no response yet!
How you go about the solution depends a lot on how particular you want to be. The PO's silicone caulk patch in the gap was tempory at best and was not the best choice of product. (There have been lots of posts on this site that silicone caulk is something that has very limited application on a boat. It really doesn't stay stuck too well and it leaves a film that later prevents anything else from sticking to the surface. I came to the same conclusion years ago around my house. Silicone caulk was messy to use and it very seldom seemed to stay soundly stuck in the gaps I wanted to seal.)
The crack/gap on your bow looks not to be at all structural; no damage to the actual hull? The bow of my boat has a similar black fiberglass fitting, although the very front is covered by the bow roller plate. If your break is not structural, you might want to try just filling the gap with a thick epoxy paste or putty. If you use putty, it looks like you should first use a standard "runny" epoxy to wet the voids a putty might not penetrate into. Then apply the putty while the surface is still wet. Some products, such as JB Weld, are naturally a very dark gray. First, brush the area liberally and repeatedly with acetone or other recommended solvent to rid the area of any silicone residue. Your exposed fiberglass looks rough enough that it should bond with epoxy without serious grinding. But sand or file away the loose fibers enough that you have a solid surface for the epoxy. Then maybe stuff some rolled-up duct tape into the gap so that it is well below the surface. This will prevent too much epoxy from squeezing down and through as you apply and/or the epoxy settling down from gravity. Then build up the gap with epoxy, spreading smooth. Wipe clean any over-flow on adjacent areas with acetone/lacquer thinner before the epoxy sets up. After the epoxy sets, repeat as needed with more epoxy if you need to build up more. After the cure, file and sand smooth. Paint to match the black surrounding area, or just paint the entire black fitting with a good quality marine polyurethane enamel. The epoxy fill will be water-tight and will be permanent.
Your repair should look plenty good. And if not totally perfect, its the bow of a boat that has seen many seasons after all.
