..perhaps for an O-ring?? Yes, the screws are likely to leak through the root of the threads, even if the hole in the gasket is undersized. Two ways to go - fill the threads in way of the shoe/hull with epoxy, or just epoxy the screws into the shoe - I'd probably do both! If the shoe and screws are both bronze, you could braze the screws into place and turn them into studs (assuming they're parallel).