Repairing larger holes in your Boston Whaler hull can be a little more involved than small dings, however, the process is still relatively simple.
First you are going to sand or grind into the hole which is actually going to make it bigger. Sand or grind away until the edges are clear and then sand all the way around the hole. For a Boston Whaler you also want to create a void behind the hole. To do this you can sand away or scrape away some of the foam so that the fiberglass is exposed inside and out. The idea is to be able to fiberglass the inside and outside of the damaged area for maximum strength. Before the next step you need to make sure the damaged area is very dry inside and out so that the epoxy will adhere.
I normally mix a batch of West Epoxy and then chop up some fiberglass cloth and mix that into the epoxy. It makes sort of a mush. It may not be pretty but it will make the repair strong. After I mix and create a mushy mixture of epoxy and cloth I push it into the hole so that it presses against the back of the hole all the way around and basically fills in the hole. You can use a stick or a screwdriver to push it into the void. You want to fill the hole up with this mixture. Then just let it set up.
After the epoxy mush sets up you should be left with a hole that is filled in but still very rough looking. To smooth out the hole just take some epoxy, thicken it with colloidal silica and spread it into the hole until it is smooth. Then you can cut some fiberglass cloth that is a little larger than the hole, mix epoxy, coat the hole and the surrounding area, lay the cloth on, coat it again and let it set up.
Then just sand the area smooth and paint it. That’s all there is too creating a very strong fiberglass repair that is actually stronger than it was before it was damaged.