Used to be that Yamaha offered a gelcoat repair kit, just for stuff like that. It was basically a mix-up type stuff, then fill the chip, then put a sealing "paper" over it to keep the air out. Once cured, peel the paper off and it was barely even noticeable. Did quite a few chips on WaveRunners with that stuff.
I've also used Plio Grip (made by Valvoline). Works good but for a good repair, it's not cheap...nor fast.
Only thing, ALL of the moisture, solvents, silicone, or wax need to be GONE out of the fibers. If not, nothing will stick to it.
https://www.youtube.com/watch?v=ogoPfYD64fQ
Pretty good vid, don't have to go through that much detail unless you want a show quality repair, but it has some good info nonetheless.
I would like to do my Yamaha cowling. Ideas are in my head but just have to get motivated to do it.