I have seen guys leave the fitting, cut the hose to about an inch or so, and clamp a bolt in there. You could also look for a round headed cap bolt and bolt that in the hole with silicone to seal it.
I just realized you said the bilge and not the bypass. Hmmmmmm. I don't think my fixes will work for the bilge outlet. Too large. You might be able to leave the fitting in and fill it with silicone.