Gelcoat - damage to bow

For small repairs, I usually sand the edges of the damaged gel coat back to clean it up using a hobby tool.  I then repair any fibreglass damage with CSM and resin being careful to stay below the gelcoat level.  Then apply a small amount of gel coat to one edge and let it cure to check colour match.  If its wrong then sand out and get pigments to suit.  I apply the gel coat to the hole and then place a sheet of OHP film over it and tape it to the hull, this helps mould the gel coat to the right profile and also give a smoothish finish.

Then its a case of sanding flush.  I start with 180 grit and work through to the finest paper I can buy.  To finish it I use rubbing compound, then t-cut then polish and it should pretty much invisable.  Try not to sand much of the existing gel coat as it will look slightly dull.

Good advice from Barty esp re the colour. Be aware that white comes in several shades! I use clear fablon (sticky back plastic) rather than OHP flim but the purpose is the same.

If this is your first go, dont expect miracles. It's a bit like plastering, your first effort will perhaps look closer to dog's dinner than dogs danglies and the sanding will test your patience (gelcoat is v hard and brittle). However, you don't mention the type of boat so I'm assuming that so long as the finish is seaworthy it'll be OK as long as it doesn't look too rough.

Also GC is thixotropic so if you are doing the repair outdoors wait for a warmer day when the stuff will cure before it sags out of shape.